Patent Description:
The present invention relates to power tools, and more specifically to rotary impact tools.

Rotary impact tools utilize a motor and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. Some rotary impact tools include an electric motor and an onboard battery for powering the electric motor.

<CIT> discloses a cordless, hand-held power tool, such as a hammer drill/driver, a drill/driver, an impact driver, an impact wrench, etc., that includes a brushless direct current ("BLDC") motor. Each of the hand-held power tool includes a removable and rechargeable battery pack, electronics, and a BLDC motor that have been designed and balanced to produce a high-performance-capable (e.g., high-power, high-current, high-torque) hand-held power tool. The hand-held power tool is capable of delivering high instantaneous (i.e., short duration) current to the BLDC motor for short-duration high power operation and high continuous (i.e., long duration) current to the BLDC motor for long duration high power operation. Additionally, the short and long duration power is capable of being provided in a smaller (in size) and lighter (in weight).

There is rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece of at least <NUM> (<NUM> ft-lbs) of fastening torque. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> pounds). A ratio of the fastening torque to the overall weight is greater than or equal to <NUM> per kg (<NUM> ft-lbs per pound).

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A peak output speed of the drive assembly to the overall weight is greater than or equal to <NUM> revolutions per minute per kilogram (<NUM> revolutions per minute per pound).

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> pounds). A ratio of peak impact frequency provided by the drive assembly to the overall weight is greater than or equal to <NUM> impacts per minute per kg (<NUM> impacts per minute per pound).

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece of at least <NUM> (<NUM> ft-lbs) of fastening torque. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> pounds). A ratio of the fastening torque to the overall weight is greater than or equal to <NUM>/kg (<NUM> ft-lbs per pound).

The present invention provides a rotary impact tool comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A mechanism efficiency of the rotary impact tool is defined as: <MAT> BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor. A first performance ratio (PR<NUM>) of the impact driver is defined as: <MAT> Inertiahammer is a moment of inertia of the hammer. The first performance ratio of the impact driver is greater than <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A mechanism efficiency of the rotary impact tool is defined as: <MAT> BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor. A second performance ratio (PR<NUM>) of the impact driver is defined as: <MAT> RPMno-load is a rotational frequency of the impact mechanism under a no-load condition and Inertiahammer is a moment of inertia of the hammer. The second performance ratio of the impact driver is greater than <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A mechanism efficiency of the rotary impact tool is defined as: <MAT> BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor. A third performance ratio (PR<NUM>) of the impact driver is defined as: <MAT> Masshammer is a mass of the hammer. The third performance ratio of the impact driver is greater than <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A mechanism efficiency of the rotary impact tool is defined as: <MAT> BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor. A fourth performance ratio (PR<NUM>) of the impact driver is defined as: <MAT> RPMno-load is a rotational frequency of the impact mechanism under a no-load condition and Masshammer is a mass of the hammer. The fourth performance ratio of the impact driver is greater than <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A mechanism efficiency of the rotary impact tool is defined as: <MAT> BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor and a voltage across the motor. A first performance ratio (PR<NUM>) of the impact driver is defined as: <MAT> Inertiahammer is a moment of inertia of the hammer. The first performance ratio of the impact driver is greater than <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A mechanism efficiency of the rotary impact tool is defined as: <MAT> BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor and a voltage across the motor. A second performance ratio (PR<NUM>) of the impact driver is defined as: <MAT> RPMno-load is a rotational frequency of the impact mechanism under a no-load condition and Inertiahammer is a moment of inertia of the hammer. The second performance ratio of the impact driver is greater than <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A mechanism efficiency of the rotary impact tool is defined as: <MAT> BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor and a voltage across the motor. A third performance ratio (PR<NUM>) of the impact driver is defined as: <MAT> Masshammer is a mass of the hammer. The third performance ratio of the impact driver is greater than <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a battery pack supported by the housing for providing power to the motor. The battery pack has a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah. The rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs). A mechanism efficiency of the rotary impact tool is defined as: <MAT> BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor and a voltage across the motor. A fourth performance ratio (PR<NUM>) of the impact driver is defined as: <MAT> RPMno-load is a rotational frequency of the impact mechanism under a no-load condition and Masshammer is a mass of the hammer. The fourth performance ratio of the impact driver is greater than <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing defining a rear of the rotary impact tool and a top of the rotary impact tool, an electric motor supported within the housing, a handle having a first end coupled to the housing and an opposite second end, a battery receptacle coupled to the second end of the handle, and a battery pack attachable to the battery receptacle. The battery pack defines a bottom of the rotary impact tool and provides power to the motor when attached to the battery receptacle. The rotary impact tool further includes a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The distal end of the anvil defines a front of the rotary impact tool. The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. A tool length is defined between the rear of the rotary impact tool and the front of the rotary impact tool. A tool height is defined between the bottom of the rotary impact tool and the top of the rotary impact tool. A ratio of the tool length to the tool height is less than or equal to <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing defining a top of the rotary impact tool, an electric motor supported within the housing, and a handle having a first end coupled to the housing and an opposite second end. The handle has a foot at the second end. The rotary impact tool further comprises a battery receptacle coupled to the foot of the handle and a battery pack attachable to the battery receptacle. The battery pack defines a bottom of the rotary impact tool and provides power to the motor when attached to the battery receptacle. The rotary impact tool further comprises a trigger on the handle to activate the motor. The trigger has a bottom lip in facing relationship with the foot of the handle. The rotary impact tool further comprises a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The distal end of the anvil defines a front of the rotary impact tool. The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. A handle height is defined between a top surface of the foot and the bottom lip of the trigger and a tool height is defined between the bottom and the top of the rotary impact tool. A ratio of the handle height to the tool height is greater than or equal to <NUM>.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil. The drive assembly also includes a spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further includes a collar having a body surrounding the anvil. The collar is moveable along the anvil between a first position, in which the tool bit is locked within the anvil, and a second position, in which the tool bit is removable from the anvil. The collar is biased towards the first position. The collar includes knurling on an outer surface of the body and a lip extending away from the rotational axis that is graspable by a user for moving the collar from the first positon to the second position.

There is another rotary impact tool not according to the invention described comprising a housing, an electric motor supported in the housing, and a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece. The drive assembly includes an anvil having an outer surface and a longitudinal bore in a distal end of the anvil configured to receive a tool bit for performing work on the workpiece. The tool bit has a bit recess. The bore defines a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil and the bore has a nominal width of <NUM> (<NUM>/<NUM> inches). The drive assembly further includes a plunger detent aperture extending radially inward from the outer surface to the bore, a bit detent aperture extending radially inward from the outer surface to the bore, a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil, and a hammer spring for biasing the hammer in an axial direction toward the anvil. The rotary impact tool further comprises a bit detent arranged in the bit detent aperture. The bit detent is moveable between a first bit detent position, in which the bit detent is at least partially in the bore, and a second bit detent position, in which the bit detent is out of the bore. The rotary impact tool further comprises a plunger in the bore. The plunger has a plunger detent recess. The rotary impact tool further comprises a plunger detent arranged in the plunger detent aperture. The plunger detent is moveable between a first plunger detent position, in which the plunger detent is at least partially in the plunger detent recess, and a second plunger detent position, in which the plunger detent is out of the plunger detent recess. The rotary impact tool further comprises a plunger spring biasing the plunger toward the distal end of the anvil, an O-ring at least partially arranged in the bit detent aperture, and a collar surrounding the anvil. The collar is moveable along the anvil between a first collar position, in which the plunger detent is inhibited by the collar from moving from the first plunger detent position to the second plunger detent position, and the bit detent is inhibited by the collar from moving from the first bit detent position to second bit detent positon, and a second collar position, in which the plunger detent is moveable by the plunger from the first plunger detent position to the second plunger detent position, and the bit detent is moveable from the first bit detent position to the second bit detent position. The collar is biased towards the first collar position. When the collar is in the second collar position and the tool bit is inserted into the bore, the O-ring is deformable by the bit detent, such that the bit detent is moveable by the bit from the first bit detent position to the second bit detent position. When the collar is in the first collar position and the tool bit is in the bore, the bit detent is in the bit recess, such that the tool bit is locked within the bore. When the collar is moved from the first collar position to the second collar position when the tool bit is in the bore, the tool bit is ejectable from the bore by the plunger.

within the scope of the appended claims.

<FIG> illustrate a power tool in the form of a rotary impact tool or impact driver <NUM>. The impact driver <NUM> includes a motor housing <NUM> in which an electric motor <NUM> is supported (<FIG>), an end cap <NUM> coupled to a rear end of the motor housing <NUM>, a gear case <NUM> at least partially housing a gear train <NUM>, and an impact housing <NUM> housing an impact mechanism <NUM>. The gear train <NUM> and impact mechanism <NUM> are part of a drive assembly <NUM> for converting a continuous torque input from the motor <NUM> to consecutive rotational impacts upon a workpiece, as described in further detail below.

The impact mechanism <NUM> includes an anvil <NUM> upon which a quick-release collar <NUM> of a bit retention assembly <NUM> is supported, which facilitates retention and removal of a tool bit <NUM> (<FIG>) from the anvil <NUM>, as described in further detail below. As also described in further detail below and shown in <FIG>, the gear train <NUM> transfers torque from the motor <NUM> to the impact mechanism <NUM>, which transfers torque to the tool bit <NUM> retained within the anvil <NUM>. As shown in <FIG> and <FIG>, the impact driver <NUM> further includes a bracket <NUM> that is removably mounted to the gear case <NUM> to secure a support member, such as a ring <NUM>, to the impact driver <NUM>, as described in further detail below.

With reference to <FIG> and <FIG>, the impact driver <NUM> also includes a handle <NUM> having a first end <NUM> coupled to the motor housing <NUM> and a second end <NUM> extending away from the motor housing <NUM>. The second end <NUM> includes a foot <NUM> having a battery receptacle <NUM> that receives a battery pack <NUM>. As shown in <FIG>, the motor housing <NUM> defines the top <NUM> of the impact driver <NUM>, and when the battery pack <NUM> is coupled to the battery receptacle <NUM>, the battery <NUM> defines the bottom <NUM> of the impact power driver <NUM>, such that an overall height H1 of the impact driver <NUM> (excluding the bracket <NUM> and ring <NUM>) is defined between the top <NUM> and bottom <NUM> of the impact driver <NUM>. A distal end of the anvil <NUM> defines the front <NUM> of the impact driver <NUM> and the end cap <NUM> defines the rear <NUM> of the impact driver <NUM>, such that an overall length L is defined between the front <NUM> and rear <NUM> of the impact driver <NUM>.

In some embodiments, the overall height H1 is <NUM> and the overall length L is <NUM>, such that a ratio of the overall length L to the overall height H is <NUM>. Because the ratio of overall length L to overall height H is less than <NUM>, the impact driver <NUM> is easier to hold and manipulate by an operator because when the operator is grasping the handle <NUM>, the operator's hand is proximate a center of gravity CG (<FIG> and <FIG>) of the impact driver <NUM>. Thus, the moment created by the center of gravity CG while the impact driver <NUM> is being held is reduced, improving the operator's control and comfort while using the impact driver <NUM>.

With continued reference to <FIG>, the handle <NUM> includes a rear side <NUM> and a trigger <NUM> that selectively electrically connects the motor <NUM> and the battery pack <NUM> to provide DC power to the motor <NUM> when the battery pack <NUM> is attached to the battery receptacle <NUM>. The trigger <NUM> has a front side <NUM> and a bottom lip <NUM> that is in facing relationship with the foot <NUM>. A minimum "trigger to back handle" distance D1 is defined between the rear side <NUM> of the handle <NUM> and the front side <NUM> of the trigger <NUM>. A handle height H2 is defined between the bottom lip <NUM> of the trigger <NUM> and a top surface <NUM> of the foot <NUM>. In some embodiments, the handle height H2 is <NUM>, such that a ratio of the handle height H2 to the overall height H1 is <NUM>. With the ratio of the handle height H2 to the overall height H1 being greater than <NUM>, the impact driver <NUM> is easier to manipulate because the handle <NUM> accounts for nearly a third or greater than a third of the overall height H1. In some embodiments, the trigger to back handle distance D1 is <NUM> or less, making the impact driver <NUM> more user friendly for operators with smaller hands.

As shown in <FIG>, the battery pack <NUM> includes a housing <NUM> enclosing a plurality of battery cells <NUM> that are electrically connected to provide the desired output (e.g., nominal voltage, current capacity, etc.) of the battery pack <NUM>. Each battery cell <NUM> may have a nominal voltage between about <NUM> Volts (V) and about <NUM> V. The battery pack <NUM> is rechargeable, and the cells may have a Lithium-based chemistry (e.g., Lithium, Lithium-ion, etc.) or any other suitable chemistry. The battery pack <NUM> has a nominal output voltage of at least <NUM> V and a nominal capacity of at least <NUM> Amp-hours (Ah) (e.g., with two strings of five series-connected battery cells (a "5S2P" pack)). In other embodiments, the impact driver <NUM> may utilize a battery pack that has a nominal capacity of at least <NUM> Ah (e.g., with three strings of five series-connected battery cells (a "5S3P pack").

The motor <NUM>, supported within the motor housing <NUM>, receives power from the battery pack <NUM> when the battery pack <NUM> is coupled to the battery receptacle <NUM> (<FIG>). The motor <NUM> is preferably a brushless direct current ("BLDC") motor with a stator <NUM> that has a plurality of stator windings <NUM> (<FIG>). The motor <NUM> also includes a rotor <NUM> having a plurality of permanent magnets (not shown). The stator <NUM> has a nominal diameter of at least <NUM> and the stator <NUM> has a stack length of at least <NUM>. For example, in one embodiment, the motor <NUM> is a BL60-<NUM> motor having a nominal diameter of <NUM> and a stack length of <NUM>. The motor <NUM> has an approximate peak power of <NUM> Watts when powered by the <NUM> Ah battery pack <NUM> (the 5S2P pack).

The rotor <NUM> is rotatable about an axis <NUM> and includes a motor output shaft <NUM> for driving the gear train <NUM>, and the impact mechanism <NUM> is coupled to an output of the gear train <NUM>. The gear train <NUM> may be configured in any of a number of different ways to provide a speed reduction between the output shaft <NUM> and an input of the impact mechanism <NUM>. With reference to <FIG>, the illustrated gear train <NUM> includes a helical pinion <NUM> formed on the motor output shaft <NUM>, a plurality of helical planet gears <NUM> meshed with the helical pinion <NUM>, and a helical ring gear <NUM> meshed with the planet gears <NUM> and rotationally fixed within the gear case <NUM>. The planet gears <NUM> are mounted on a camshaft <NUM> of the impact mechanism <NUM> such that the camshaft <NUM> functions as a planet carrier. Accordingly, rotation of the output shaft <NUM> rotates the planet gears <NUM>, which then rotate along the inner circumference of the ring gear <NUM> and thereby rotate the camshaft <NUM>. The output shaft <NUM> is rotatably supported by a first or forward bearing <NUM> and a second or rear bearing <NUM> that is supported by the end cap <NUM>.

The impact mechanism <NUM> of the impact driver <NUM> will now be described with reference to <FIG>. The impact mechanism <NUM> includes the anvil <NUM>, which extends from the impact housing <NUM>. As noted above, the tool bit <NUM> can be coupled to the anvil <NUM> for performing work on a workpiece (e.g., a fastener). The impact mechanism <NUM> is configured to convert the continuous rotational force or torque provided by the motor <NUM> and gear train <NUM> to a striking rotational force or intermittent applications of torque to the anvil <NUM> when the reaction torque on the anvil <NUM> (e.g., due to engagement between the tool element and a fastener being worked upon) exceeds a certain threshold. In the illustrated embodiment of the impact driver <NUM>, the impact mechanism <NUM> includes the camshaft <NUM>, a hammer <NUM> supported on and axially slidable relative to the camshaft <NUM>, and the anvil <NUM>.

The impact mechanism <NUM> further includes a hammer spring <NUM> biasing the hammer <NUM> toward the front of the impact driver <NUM> (i.e., toward the right in <FIG>). In other words, the hammer spring <NUM> biases the hammer <NUM> in an axial direction toward the anvil <NUM>, along the axis <NUM>. A thrust bearing <NUM> and a thrust washer <NUM> are positioned between the hammer spring <NUM> and the hammer <NUM>. The thrust bearing <NUM> and the thrust washer <NUM> allow for the hammer spring <NUM> and the camshaft <NUM> to continue to rotate relative to the hammer <NUM> after each impact strike when lugs <NUM> (<FIG>) on the hammer <NUM> engage with corresponding anvil lugs <NUM> and rotation of the hammer <NUM> momentarily stops.

The camshaft <NUM> further includes cam grooves <NUM> in which corresponding cam balls <NUM> are received (<FIG>). The cam balls <NUM> are in driving engagement with the hammer <NUM> such that movement of the cam balls <NUM> within the cam grooves <NUM> allows for relative axial movement of the hammer <NUM> along the camshaft <NUM> when the hammer lugs <NUM> and the anvil lugs <NUM> are engaged, rotation of the anvil <NUM> is seized, and the camshaft <NUM> continues to rotate.

In other embodiments (not shown), the impact mechanism includes a cylinder coupled to the electric motor <NUM> to receive torque therefrom, causing the cylinder to rotate. The cylinder at least partially defines a chamber that contains an incompressible fluid (e.g., hydraulic fluid, oil, etc.). The hydraulic fluid in the chamber reduces the wear and the noise of the impact assembly that is created by impacting the hammer and the anvil. The hammer and anvil are both positioned at least partially within the chamber. The hammer includes an aperture to permit the hydraulic fluid in the chamber to pass through the hammer. A hammer spring biases the hammer toward the anvil. Such an impact mechanism is described in <CIT>.

The bit retention assembly <NUM> of the impact driver <NUM> will now be described with reference to <FIG>. Specifically, the distal end of the anvil <NUM> includes a longitudinal bore <NUM> in which the tool bit <NUM> is receivable. As shown in <FIG>, the bore <NUM> has a hexagonal cross-sectional shape in a plane oriented transverse to the axis <NUM>, and has a nominal width <NUM> of <NUM> (<NUM>/<NUM> inches) to receive the tool bit <NUM>, which has a corresponding nominal width of <NUM> (<NUM>/<NUM> inches). The anvil <NUM> also includes a single radial slot <NUM> that extends from the longitudinal bore <NUM> through the anvil <NUM>. The bit retention assembly <NUM> includes a ball detent <NUM> received in the radial slot <NUM>, the collar <NUM> slidably disposed on the anvil <NUM>, a collar spring <NUM> that biases the collar <NUM> in a rearward direction to a first collar position (<FIG>, <FIG>, and <FIG>), and a washer <NUM> and retaining ring <NUM> that maintain the collar spring <NUM> on the anvil <NUM>. The collar <NUM> includes a body portion <NUM> including knurling <NUM> on an outer surface thereof. The collar <NUM> also includes an annular lip <NUM> arranged on a distal end of the collar <NUM> that is farthest from the impact housing <NUM>. The lip <NUM> extends away from body portion <NUM> and the axis <NUM> so as to form a flared portion of the collar <NUM>.

The collar <NUM> also includes an interior ring <NUM> having an inner diameter sized to maintain at least a portion of the ball detent <NUM> within the longitudinal bore <NUM> which, in turn, is received within a circumferential groove <NUM> of the tool bit <NUM> (<FIG>) to secure the tool bit <NUM> within the anvil <NUM>. The bit retention assembly <NUM> also includes a detent spring <NUM> positioned around the anvil <NUM>. A U-shaped finger <NUM> of the detent spring <NUM> is received within the slot <NUM> for biasing the ball detent <NUM> toward the front of the slot <NUM> and toward the open end of the longitudinal bore <NUM>. The collar <NUM> is moveable along the anvil <NUM> between the first collar position (<FIG>, <FIG>, and <FIG>) and a second collar position (<FIG>), in which the collar <NUM> is pulled forwardly along the anvil <NUM> against the bias of the collar spring <NUM> until the interior ring <NUM> moves forward of the ball detent <NUM>, such that a recess <NUM> rearward of the interior ring <NUM> is axially aligned with the ball detent <NUM>.

In operation, to secure the tool bit <NUM> within the anvil <NUM>, while the collar <NUM> is in the first collar position, an operator needs only to insert the end of the tool bit <NUM> having the circumferential groove <NUM> within the longitudinal bore <NUM> and push the tool bit <NUM> toward the ball detent <NUM>. Continued insertion of the tool bit <NUM> causes the tool bit <NUM> to engage the ball detent <NUM> and push the ball detent <NUM> rearward against the bias of the detent spring <NUM>. After the ball detent <NUM> is pushed far enough to clear the interior ring <NUM> on the collar <NUM>, the ball detent <NUM> is pushed radially outwardly in the slot <NUM> and into the recess <NUM> by the tool bit <NUM>. The tool bit <NUM> may then slide under the ball detent <NUM> until the ball detent <NUM> is received within the circumferential groove <NUM> in the tool bit <NUM>, at which time the detent spring <NUM> at least partially rebounds to push the ball detent <NUM> underneath the interior ring <NUM>. Since the collar <NUM> is not required to be moved to the second collar position to secure the tool bit <NUM> within the anvil <NUM>, the operator of the impact driver <NUM> needs only to use a single hand to insert and secure the tool bit <NUM> within the anvil <NUM>.

To release the tool bit <NUM>, the operator may grasp the knurling <NUM> on the body portion <NUM> and/or the lip <NUM> of the collar <NUM> to move the collar <NUM> from the first collar position to the second collar position, such that the recess <NUM> is axially aligned with the ball detent <NUM>. The tool bit <NUM> may then be pulled from the anvil <NUM>, during which time the tool bit <NUM> forces the ball detent <NUM> to displace radially outwardly into the recess <NUM>. Once the tool bit <NUM> has moved passed the ball detent <NUM>, the detent spring <NUM> at least partially rebounds to push the ball detent <NUM> underneath the interior ring <NUM>. The operator may then release the collar <NUM>, allowing the collar spring <NUM> to return the collar <NUM> to the first collar position. The knurling <NUM> enhances the operator's grip on the collar <NUM> by permitting more friction to be developed between the collar <NUM> and the operator's fingers when grasping the collar <NUM>. Similarly, the lip <NUM> facilitates the operator's grasp the collar <NUM> for moving it from the first collar position to the second collar position because the lip <NUM> provides a flared portion against which the operator can apply force in a direction parallel to the axis <NUM>.

As noted above, the bracket <NUM> is removably mounted to the gear case <NUM> to secure the ring <NUM> to the impact driver <NUM>. With reference to <FIG> and <FIG>, the gear case <NUM> includes an upwardly-extending mounting portion <NUM> that is arranged between the motor housing <NUM> and the impact housing <NUM>. The mounting portion <NUM> includes a pair of mounting bores <NUM> extending through a mounting surface <NUM>. The mounting portion <NUM> protrudes radially through the motor housing <NUM> such that the bores <NUM> are exposed to the exterior of the impact driver <NUM>. As shown in <FIG> and <FIG>, the bracket <NUM> can be removably coupled to the mounting portion <NUM> via a pair of bracket fasteners <NUM>. Before fastening the bracket <NUM> to the mounting portion <NUM>, the ring <NUM> can be arranged between the bracket <NUM> and the mounting surface <NUM>. The ring <NUM> is configured to receive a lanyard <NUM> (<FIG>) that is attached to a user's belt, for example, to tether the impact driver <NUM> to the user. As such, the lanyard <NUM>, ring <NUM>, and bracket <NUM> will cooperate to prevent the impact driver <NUM> from hitting the ground if dropped by the operator. The ring <NUM> is configured to pivot within the bracket <NUM>, providing flexibility in how the lanyard <NUM> tethers the impact driver <NUM> to the operator.

As shown in <FIG>, four housing fasteners <NUM> extend respectively, in the following order, through each of the impact housing <NUM>, the gear case <NUM>, and the motor housing <NUM>, starting through the impact housing <NUM> and terminating in the motor housing <NUM>. In this manner, the motor housing <NUM> is coupled to the impact housing <NUM> and the gear case <NUM> is secured (i.e., clamped) between the motor housing <NUM> and the impact housing <NUM>. Because the bracket <NUM> is secured to the mounting portion <NUM> with only the bracket fasteners <NUM>, removal of the housing fasteners <NUM> that join the motor housing <NUM> and gear case <NUM> to the impact housing <NUM> is not required to remove the bracket <NUM> from the mounting portion <NUM>. This arrangement thus affords the operator greater convenience when removing the bracket <NUM> to service or remove the ring <NUM>. Also, because the bracket <NUM> is not secured to the impact driver <NUM> via the housing fasteners <NUM>, the bracket <NUM> is more easily shared across different tools having an arrangement of mounting bores that are similar to the arrangement of the mounting bores <NUM> of the mounting portion <NUM>.

In operation of the impact driver <NUM>, the operator first inserts the tool bit <NUM> into the anvil <NUM>, as described above. The operator then depresses the trigger switch <NUM> to activate the motor <NUM>, which continuously drives the gear train <NUM> and the camshaft <NUM> via the output shaft <NUM>. As the camshaft <NUM> rotates, the cam balls <NUM> drive the hammer <NUM> to co-rotate with the camshaft <NUM>, and the hammer lugs <NUM> engage, respectively, driven surfaces of the anvil lugs <NUM> to provide an impact and to rotatably drive the anvil <NUM> and the tool bit <NUM>. After each impact, the hammer <NUM> moves or slides rearward along the camshaft <NUM>, away from the anvil <NUM>, so that the hammer lugs <NUM> disengage the anvil lugs <NUM>. The hammer spring <NUM> stores some of the rearward energy of the hammer <NUM> to provide a return mechanism for the hammer <NUM>. After the hammer lugs <NUM> disengage the respective anvil lugs <NUM>, the hammer <NUM> continues to rotate and moves or slides forwardly, toward the anvil <NUM>, as the hammer spring <NUM> releases its stored energy, until the drive surfaces of the hammer lugs <NUM> re-engage the driven surfaces of the anvil lugs <NUM> to cause another impact. As defined herein, "impact frequency" means the number of impacts imparted by the hammer <NUM> upon the anvil <NUM> per unit time, measured in "impacts per minute. " Once finished with the impact driving operation, the operator may remove the tool bit <NUM> from the anvil <NUM>, as described above.

During operation of the impact driver <NUM> under a no-load condition, when the anvil <NUM> is not being used to apply torque to a fastener, the co-rotation of the camshaft <NUM>, the hammer <NUM>, and the anvil <NUM> define an "output speed" of the impact driver <NUM> measured in revolutions per minute.

The impact driver <NUM> has a weight of <NUM> pounds, the <NUM> Ah battery pack <NUM> (the 5S2P pack) has a weight of <NUM> pounds, and the <NUM> Ah battery pack (5S3P) has a weight of <NUM> pounds. Thus, when the 5Ah battery pack <NUM> is coupled to the impact driver <NUM>, the impact driver <NUM> has an overall weight of <NUM> pounds, and when the <NUM> Ah battery pack is coupled to the impact driver <NUM>, the impact driver <NUM> has an overall weight of <NUM> pounds. As defined herein, the term "fastening torque" means torque applied to a fastener in a direction increasing tension (i.e. in a tightening direction).

The first and second rows of TABLE <NUM> below list the overall weight, the peak output speed, the peak fastening torque, and the peak impact frequency (measured in impacts per minute) achieved by known prior art <NUM> (<NUM>/<NUM> inch) impact wrenches that use a 5Ah battery pack. The third and fourth rows of TABLE <NUM> below list the peak output speed, the peak fastening torque, and the peak impact frequency achieved by the impact driver <NUM> when respectively using the battery pack <NUM> (the 5S2P pack - <NUM> Ah) or the 5S3P (<NUM> Ah) battery pack. The peak fastening torque is measured by fastening a <NUM>-<NUM>/<NUM>" zinc plated, Grade <NUM> bolt. TABLE <NUM> below also lists the ratios of peak output speed to overall weight, calculated by dividing peak output speed by the overall weight. TABLE <NUM> below also lists the ratio of peak fastening torque to overall weight, calculated by dividing the peak fastening torque by the overall weight. TABLE <NUM> below also lists the ratio of peak impact frequency to the overall weight, calculated by dividing the peak impact frequency by the overall weight.

As shown in TABLE <NUM>, when using the <NUM> Ah battery pack <NUM>, and with a motor <NUM> capable of generating approximately <NUM> Watts of power with a stator <NUM> having a nominal diameter of only <NUM> and a stack length of only <NUM>, the impact driver <NUM> is capable of achieving a higher ratio of peak output speed to overall weight than either of the prior art impact wrenches while having a lower overall weight than either of the prior art impact wrenches.

Also, as shown in TABLE <NUM>, when using the <NUM> Ah battery pack <NUM>, and with a motor <NUM> capable of generating approximately <NUM> Watts of power with a stator <NUM> having a nominal diameter of only <NUM> and a stack length of only <NUM>, the impact driver <NUM> achieves nearly the same ratio of peak fastening torque to overall weight as the prior art impact wrenches, while having a lower overall weight than the prior art impact wrenches. Therefore, on a per-unit weight basis, the impact driver <NUM> approximately matches the fastening torque performance of the heavier prior art impact wrenches.

Further, as shown in TABLE <NUM>, when using the 5Ah battery pack <NUM>, and with a motor <NUM> capable of generating approximately <NUM> Watts of power with a stator <NUM> having a nominal diameter of only <NUM> and a stack length of only <NUM>, the impact driver <NUM> achieves a higher ratio of impact frequency to overall weight than the prior art impact wrenches, while having a lower overall weight than the prior art impact wrenches. Thus, the impact driver <NUM> provides an operator with a lighter weight rotary impact tool for jobs while still achieving the nearly the same or better fastening performance characteristics than other known prior art <NUM> (<NUM>/<NUM>-inch) impact wrenches.

As used herein, the term "mechanism efficiency" ("ηa") represents how well an impact driver produces work per unit of time per input unit of power. The mechanism efficiency is determined by multiplying the impact frequency, measured in impacts per minute ("BPM") by the kinetic energy of the hammer <NUM> during a loaded condition and prior to impact with the anvil <NUM> ("KE Hammer, Drilling", measured in Joules) divided by current drawn by the motor <NUM> ("Current motor", measured in Amperes) and the voltage across the motor <NUM> ("Voltage motor", measured in Volts), as shown in the below equation: <MAT>.

When using the <NUM> Ah battery pack <NUM>, and with a motor <NUM> capable of generating approximately <NUM> Watts of power with a stator <NUM> having a nominal diameter of only <NUM> and a stack length of only <NUM>, the impact driver <NUM> is capable of achieving a variety of advantageous performance ratios, as described below.

For example, a first performance ratio ("PR<NUM>") measures the efficiency of the impact mechanism <NUM> per unit of inertia of the hammer <NUM>. The first performance ratio is determined by dividing the mechanism efficiency by the moment of inertia of the hammer <NUM> ("Inertia hammer", measured in kg-m<NUM>) and a scaler of <NUM>,<NUM>, as shown in the below equation: <MAT>.

The scaler of <NUM>/<NUM>,<NUM> is used to reduce the first performance ratio to a manageable number of significant digits (e.g., three, as shown in Table <NUM> below). However, other scalers could be used.

A second performance ratio ("PR<NUM>") measures the ability of the impact mechanism <NUM> to maintain the level at which it's performing work during a transition from a no-load state to a loaded state, per unit of inertia of the hammer <NUM>. Specifically, the second performance ratio is determined by multiplying the mechanism efficiency times the rotational frequency, measured in revolutions per minute, of the impact mechanism <NUM> under a no-load condition ("RPM no-load") divided by the moment of inertia of the hammer <NUM> and a scaler of <NUM>,<NUM>,<NUM>, as shown in the below equation: <MAT>.

The scaler of <NUM>/<NUM>,<NUM>,<NUM> is used to reduce the second performance ratio to a manageable number of significant digits (e.g., three, as shown in Table <NUM> below). However, other scalers could be used.

A third performance ratio ("PR<NUM>") measures the efficiency of the impact mechanism <NUM> per unit of mass of the hammer <NUM>. The third performance ratio is determined by dividing the mechanism efficiency by the mass of the hammer <NUM> ("Mass hammer", measured in kg) and a scaler of <NUM>, as shown in the below equation: <MAT>.

The scaler of <NUM>/<NUM> is used to reduce the third performance ratio to a manageable number of significant digits (e.g., three, as shown in Table <NUM> below). However, other scalers could be used.

A fourth performance ratio ("PR<NUM>") measures the ability of the impact mechanism <NUM> to maintain the level at which it's performing work during a transition from a no-load state to a loaded state, per unit of mass of the hammer <NUM>. Specifically, the fourth performance ratio is determined by multiplying the mechanism efficiency times the rotational frequency, measured in revolutions per minute, of the impact mechanism <NUM> under a no-load condition divided by the mass of the hammer <NUM> and a scaler of <NUM>, as shown in the below equation: <MAT>.

The scaler of <NUM>/<NUM>,<NUM> is used to reduce the third performance ratio to a manageable number of significant digits (e.g., four, as shown in Table <NUM> below). However, other scalers could be used.

The first and second rows of TABLE <NUM> below list values for impact frequency (measured in impacts per minute), hammer kinetic energy (J), voltage (V), current (A), no-load speed (RPM), hammer inertia (kg-s2), hammer mass (kg), as well as the first, second, third, and fourth performance ratios respectively achieved by the first and second prior art <NUM> (<NUM>/<NUM>)-inch impact wrenches discussed in TABLE <NUM> above, using a 5Ah battery pack in a drilling operation. The third row lists the same values for a third prior art <NUM> (<NUM>/<NUM>-inch) impact wrench using a 5Ah battery pack in a drilling operation. The fourth and fifth rows of TABLE <NUM> below list the same values for the impact driver <NUM> when respectively using the battery pack <NUM> (the 5S2P pack - <NUM> Ah) or the 5S3P (<NUM> Ah) battery pack.

As can be seen in TABLE <NUM>, as compared with the three prior art <NUM>/<NUM>" impact wrenches using a 5Ah battery pack in a drilling operation, the impact driver <NUM> with the 5Ah battery pack <NUM> is the only <NUM> (<NUM>/<NUM>-inch) impact driver able to achieve a first performance ratio that is greater than <NUM>, a second performance ratio that is greater than <NUM>, a third performance ratio that is greater than <NUM>, and a fourth performance ratio that is greater than <NUM>. Similarly, the impact driver <NUM> when using a 9Ah battery pack in a drilling operation is able to achieve a first performance ratio that is greater than <NUM>, a second performance ratio that is greater than <NUM>, a third performance ratio that is greater than <NUM>, and a fourth performance ratio that is greater than <NUM>.

With respect to the first and third performance ratios, while the three prior art <NUM> (<NUM>/<NUM>-inch) impact drivers benefit from larger hammers than the impact driver <NUM> with respect to peak fastening torque (see TABLE <NUM>), they are penalized in evaluation of the first and third performance ratios because the larger hammers also result in a higher moment of inertia. Because the impact driver <NUM> has a smaller and lighter hammer <NUM> yet still achieves a comparable mechanism efficiency as the three prior art <NUM> (<NUM>/<NUM>-inch) impact drivers, it achieves a first performance ratio that is greater than <NUM> and a third performance ratio that is greater than <NUM> because the moment of inertia of the hammer <NUM> is lower (relevant to the first performance ratio) due to the smaller and lighter hammer <NUM> (relevant to the third performance ratio). Thus, the efficiency of the impact mechanism <NUM> per unit of inertia of the hammer <NUM> of the impact driver <NUM> (first performance ratio) or per unit of mass of the hammer <NUM> (third performance ratio) is greater than the three prior art <NUM> (<NUM>/<NUM>-inch) impact drivers.

With respect to the second and fourth performance ratios, impact drivers that have a high no-load speed (at the beginning of an operation) and a high loaded speed (as evaluated by the kinetic energy of the hammer <NUM> in a loaded state, prior to impact) are favored, because during a drilling or fastening operation, it is advantageous for the impact mechanism <NUM> to possess both high initial (unloaded) speed and a high speed when in a loaded state (during the operation) that is continued through termination of the operation. Because the impact driver <NUM> has a smaller hammer <NUM> yet still achieves a higher no-load speed than the three prior art <NUM> (<NUM>/<NUM>-inch) impact drivers, it achieves a second performance ratio that is greater than <NUM> and a fourth performance ratio that is greater than <NUM>. Thus, the impact mechanism <NUM> of the impact driver <NUM> is better able to maintain the level at which it's performing work during a transition from a no-load state to a loaded state, per unit of inertia of the hammer <NUM> (second performance ratio) or per unit of mass of the hammer <NUM> (fourth performance ratio), compared to the three prior art <NUM> (<NUM>/<NUM>-inch) impact drivers identified in TABLE <NUM> above.

The impact driver <NUM> is particularly effective at drilling operations because it simultaneously achieves a first performance ratio that is greater than <NUM>, a second performance ratio that is greater than <NUM>, a third performance ratio that is greater than <NUM>, and a fourth performance ratio that is greater than <NUM>.

An alternative embodiment of a bit retention assembly <NUM> for the impact driver <NUM> will now be described with reference to <FIG>. A distal end <NUM> of an anvil <NUM> includes a longitudinal bore <NUM> in which the tool bit <NUM> is receivable. Like the bore <NUM> of the anvil <NUM>, the bore <NUM> of the anvil <NUM> has a hexagonal cross-sectional shape in a plane oriented transverse to the axis <NUM>, and has a nominal width of <NUM> (<NUM>/<NUM> inches) to receive the tool bit <NUM>. The anvil <NUM> has an outer surface <NUM> and a circumferential groove <NUM> (<FIG>) for receipt of a clip <NUM> (<FIG> and <FIG>). A bearing <NUM> is also arranged on the outer surface <NUM> for rotatably supporting the anvil <NUM> within the impact housing <NUM>. In some embodiments, the bearing <NUM> is press-fit to the anvil <NUM>. The anvil <NUM> also has a circumferential O-ring groove <NUM> (<FIG>) in which an O-ring <NUM> (<FIG> and <FIG>) is retained.

The anvil <NUM> further includes a pair of radial plunger detent apertures <NUM> and a radial bit detent aperture <NUM>, all of which extend radially inward from the outer surface <NUM> to the bore <NUM> (<FIG>). The bit detent aperture <NUM> intersects the O-ring groove <NUM>, such that the O-ring <NUM> is at least partially arranged in the bit detent aperture <NUM>. As shown in <FIG> and <FIG>, a pair of plunger detents <NUM> are respectively arranged in the plunger detent apertures <NUM> and a bit detent <NUM> is arranged in the bit detent aperture <NUM>. As shown in <FIG> and <FIG>, a plunger <NUM> is arranged in the bore <NUM> and is biased toward the distal end <NUM> of the anvil <NUM> by a plunger spring <NUM> that is also arranged in the bore <NUM>. The plunger <NUM> includes a circumferential plunger detent recess <NUM>.

The bit retention assembly <NUM> includes the O-ring <NUM>, the bit detent <NUM> received in the bit detent aperture <NUM>, a collar <NUM> slidably disposed on the anvil <NUM>, a collar spring <NUM> that biases the collar <NUM> in a rearward direction to a first collar position (<FIG> and <FIG>), and a washer <NUM> that maintains the collar spring <NUM> on the anvil <NUM>. As shown in <FIG> and <FIG>, the washer <NUM> is arranged between the O-ring <NUM> and the collar spring <NUM>, with the washer <NUM> being abutted with the O-ring <NUM>. As shown in <FIG>, the collar <NUM> may include ribs <NUM> on an outer surface <NUM> thereof to enhance the operator's grip on the collar <NUM>. The clip <NUM> limits the extent to which the collar spring <NUM> can push the collar <NUM> rearward, such that the first position is defined by the collar <NUM> being abutted against the clip <NUM>, as shown in <FIG> and <FIG>.

The collar <NUM> includes a first inner plunger detent surface <NUM> and a second inner plunger detent surface <NUM> that has a greater diameter than the first inner plunger detent surface <NUM>. The collar <NUM> also includes a first inner bit detent surface <NUM> and a second inner bit detent surface <NUM> that has a greater diameter than the first inner bit detent surface <NUM>. In the first collar position (<FIG> and <FIG>), the first inner plunger detent surface <NUM> is axially aligned with the plunger detent apertures <NUM>, such that the plunger detents <NUM> are radially inhibited by the first inner plunger detent surface <NUM>, and the first inner bit detent surface <NUM> is axially aligned with the bit detent aperture <NUM>. As shown in <FIG>, when the collar <NUM> is in the first collar position, the plunger spring <NUM> is maintained in a compressed state by virtue of the plunger detents <NUM> being inhibited from moving in a radially outward direction by the first inner plunger detent surface <NUM>. Thus, the plunger detents <NUM> are maintained in the plunger detent recess <NUM>, keeping the plunger <NUM> axially loaded against the plunger spring <NUM>.

The collar <NUM> is moveable along the anvil <NUM> between the first collar position (<FIG> and <FIG>) and a second collar position (<FIG>), in which the collar <NUM> is pulled forwardly along the anvil <NUM> against the bias of the collar spring <NUM> until the first inner plunger detent surface <NUM> is axially forward of the plunger detent apertures <NUM>, the second inner plunger detent surface <NUM> is axially aligned with the plunger detent apertures <NUM>, the first inner bit detent surface <NUM> is axially forward of the bit detent aperture <NUM>, and the second inner bit detent surface <NUM> is axially aligned with the bit detent aperture <NUM>.

In operation, to secure the tool bit <NUM> within the anvil <NUM>, while the collar <NUM> is in the second collar position (<FIG>), an operator needs only to insert the end of the tool bit <NUM> having the circumferential groove <NUM> within the longitudinal bore <NUM> and push the tool bit <NUM> toward the plunger <NUM>. Continued insertion of the tool bit <NUM> causes the tool bit <NUM> to engage the bit detent <NUM> and push the bit detent <NUM> radially outward in the bit detent aperture <NUM> until it abuts the first inner bit detent surface <NUM>, causing the O-ring <NUM> to elastically deform until the bit detent <NUM> is pushed out of the longitudinal bore <NUM>. Once the bit detent <NUM> is pushed out of the longitudinal bore, the tool bit <NUM> may then slide past the bit detent <NUM> until the bit detent <NUM> is axially aligned with the circumferential groove <NUM> in the tool bit <NUM>, at which time the O-ring <NUM> elastically recovers to push the bit detent <NUM> into the circumferential groove <NUM>. The tool bit <NUM> is then locked within the bore <NUM>.

As the tool bit <NUM> moves rearwardly in the longitudinal bore <NUM>, the tool bit <NUM> also pushes the plunger <NUM> rearward, compressing the plunger spring <NUM>, such that the plunger detents <NUM> become axially aligned with the plunger detent recess <NUM>. The collar spring <NUM> is thus allowed to push the collar <NUM> rearward, causing the plunger detents <NUM> to be pushed into the plunger detent recess <NUM>. The collar spring <NUM> then continues pushing the collar <NUM> rearward until the first inner plunger detent surface <NUM> becomes axially aligned with the plunger detent apertures <NUM> and the collar <NUM> is in the first collar position. Since the operator does not need to manually move the collar <NUM> from the second collar position to the first collar position (<FIG>) to secure the tool bit <NUM> within the anvil <NUM>, the operator of the impact driver <NUM> needs only to use a single hand to insert and secure the tool bit <NUM> within the anvil <NUM>.

To release the tool bit <NUM>, the operator moves move the collar <NUM> from the first collar position to the second collar position. The ribs <NUM> facilitate the operator's grasp on the collar <NUM> moving it from the first collar position to the second collar position because the ribs <NUM> provide flared portions against which the operator can apply force in a direction parallel with the axis <NUM>. Movement of the collar <NUM> to the second collar position causes the second inner plunger detent surface <NUM> to be axially aligned with the plunger detent apertures <NUM> and the second inner bit detent surface <NUM> to be axially aligned with the bit detent aperture <NUM>.

Because the plunger detents <NUM> are no longer radially constrained by the first inner plunger detent surface <NUM>, the plunger spring <NUM> is able to rebound, pushing the plunger <NUM> toward the distal end <NUM> of the anvil <NUM>, thus causing the plunger detents <NUM> to be moved radially outward in the plunger detent apertures <NUM> until they are out of the plunger detent recess <NUM> and abutting the second inner plunger detent surface <NUM> of the collar <NUM>. Because the bit detent <NUM> is no longer radially constrained by the first inner bit detent surface <NUM>, the tool bit <NUM> is no longer locked within the bore <NUM> and thus the plunger <NUM> ejects the tool bit <NUM> from the bore <NUM>.

As the tool bit <NUM> is ejected from the bore <NUM> by the plunger <NUM>, the bit detent <NUM> is pushed by the tool bit <NUM> radially outward in the bit detent aperture <NUM> until it abuts the second inner bit detent surface <NUM>. As the bit detent <NUM> is pushed radially outward by the tool bit <NUM>, the movement of the bit detent <NUM>, and thus the movement of the tool bit <NUM> as it is exiting the bore <NUM>, is resisted by the O-ring <NUM>, because the bit detent <NUM> must frictionally engage the o-ring <NUM> as it is moved toward the second inner bit detent surface <NUM>. Because the O-ring <NUM> resists the movement of the tool bit <NUM> from the bore <NUM>, the tool bit <NUM> is prevented from suddenly ejecting from the bore <NUM> when the collar <NUM> is moved to the second collar position. Thus, it is easier for an operator to grasp or retain the tool bit <NUM> as it is ejected from the bore <NUM>.

The operator may then release the collar <NUM>. When the collar <NUM> is released, the collar <NUM> is maintained in the second position by virtue of the plunger spring <NUM> keeping the plunger <NUM> pushed forward, such that the plunger detents <NUM> are maintained against an intermediate flat <NUM> of the plunger <NUM>, the diameter of which is greater than the plunger detent recess <NUM>. Thus, the plunger detents <NUM> are maintained against the second inner plunger detent surface <NUM> of the collar <NUM>, thereby preventing the collar spring <NUM> from returning the collar <NUM> to the first collar position. The collar <NUM> is thus maintained in the second collar position, ready for reinsertion of the tool bit <NUM>, as described above.

Claim 1:
A rotary impact tool (<NUM>) comprising:
a housing (<NUM>);
an electric motor (<NUM>) supported in the housing;
a drive assembly (<NUM>) for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece of at least <NUM> (<NUM> ft-lbs) of fastening torque, the drive assembly including
an anvil (<NUM>, <NUM>) having a bore (<NUM>, <NUM>) in a distal end (<NUM>) thereof for receipt of the workpiece or a tool bit (<NUM>) for performing work on the workpiece, the bore defining a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil, the bore having a nominal width of <NUM> (<NUM>/<NUM> inches),
a hammer (<NUM>) that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil, and
a spring (<NUM>) for biasing the hammer in an axial direction toward the anvil;
a battery pack (<NUM>) supported by the housing for providing power to the motor, the battery pack having a nominal voltage of at least <NUM> Volts and a nominal capacity of at least <NUM> Ah;
wherein the rotary impact tool has an overall weight including the battery pack that is less than or equal to <NUM> (<NUM> lbs), and
wherein a ratio of the fastening torque to the overall weight is greater than or equal to <NUM> per kg (<NUM> ft-lbs per pound),
wherein a mechanism efficiency of the rotary impact tool is defined as: <MAT>
wherein BPM is the number of impacts per minute, KEHammer, Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor,
wherein a first performance ratio (PR<NUM>) of the rotary impact tool is defined as: <MAT>
wherein Inertiahammer is a moment of inertia of the hammer, and
wherein the first performance ratio of the rotary impact tool is greater than <NUM>.