Patent Description:
The present invention relates to power tools, and more particularly to rotary impact tools, such as impact wrenches and even more particularly to a power tool according to the preamble of claim <NUM> and a power tool according to the preamble of claim <NUM>.

Rotary impact tools are typically utilized to provide a striking rotational force, or intermittent applications of torque, to a tool element or workpiece (e.g., a fastener) to either tighten or loosen the fastener. In <CIT> a rotary impact-type powered screw or nut drive has a clutch between a motor and a hammer drive spindle which can be set to open at a desired torque limit depending on a size of the screw or nut. <CIT> discloses a power tool according to the preamble of claim <NUM> and a power tool according to the preamble of claim <NUM>.

The present invention provides, in one aspect, a power tool, according to claim <NUM>, including a housing having a first housing portion and a second housing portion coupled to the first housing portion, a motor directly mounted within the housing between the first and second housing portions and including an output shaft, the output shaft defining an axis, a gear assembly supported within the housing and operably coupled to the motor, the gear assembly including a ring gear directly supported by the first and second housing portions, a pinion gear coupled for co-rotation with the output shaft, and a plurality of planet gears meshed with the pinion gear and the ring gear. The power tool also includes a drive assembly operably coupled to the gear assembly, the drive assembly including a camshaft, an anvil, a hammer configured to reciprocate along the camshaft to impart rotational impacts to the anvil in response to rotation of the camshaft, and a spring biasing the hammer towards the anvil. The ring gear includes a plurality of lugs engaged with the first housing portion and the second housing portion to rotationally constrain the ring gear.

The present invention provides, in another aspect, a power tool, according to claim <NUM>, including a housing having a motor housing portion and a handle portion extending from the motor housing portion, the motor housing portion and the handle portion defined by cooperating first and second clamshell halves coupled together along a parting plane, a motor supported within the motor housing portion and including an output shaft, the output shaft defining an axis, and a gear assembly supported within the housing and operably coupled to the motor, the gear assembly including a ring gear directly supported by the first and second clamshell halves, a pinion gear coupled for co-rotation with the output shaft, and a plurality of planet gears meshed with the pinion gear and the ring gear. The power tool also includes a drive assembly operably coupled to the gear assembly, the drive assembly including a camshaft, an anvil, a hammer configured to reciprocate along the camshaft to impart rotational impacts to the anvil in response to rotation of the camshaft, and a spring biasing the hammer towards the anvil. The ring gear includes a plurality of lugs engaged with the first and second clamshell halves to rotationally constrain the ring gear, and the plurality of lugs is arranged such that all resultant force vectors on the first and second clamshell halves due to torque on the ring gear are oriented at an angle between <NUM> degrees and <NUM> degrees relative to the parting plane.

The present disclosure provides, in another aspect, a power tool including a housing having a first housing portion and a second housing portion coupled to the first housing portion, a motor directly mounted within the housing between the first and second housing portions and including an output shaft, the output shaft defining an axis, a gear assembly supported within the housing and operably coupled to the motor, the gear assembly including a ring gear and a pinion gear coupled to the output shaft, and a drive assembly operably coupled to the gear assembly, the drive assembly including a camshaft, an anvil, and a hammer configured to reciprocate along the camshaft to impart rotational impacts to the anvil in response to rotation of the camshaft. The camshaft includes a bore through which an extension of the pinion gear extends. A pinion seal is supported on the pinion gear, the pinion seal including a flange configured to seal at least one selected from a group consisting of a first interface between the pinion gear and the camshaft and a second interface between the camshaft and the ring gear.

The present disclosure provides, in another aspect, a power tool comprising:.

The spring may have a rectangular cross-section.

The camshaft may include a bore, wherein the pinion gear may be meshed with the planet gears within the bore, wherein the pinion gear may include an extension extending into the bore beyond the planet gears, wherein a bearing may be supported within the bore, and wherein the bearing may support the extension of the pinion gear.

The housing, the spring, the camshaft, the bearing, and the extension may overlap along the axis such that a plane perpendicular to the axis intersects the housing, the spring, the camshaft, the bearing, and the extension.

The power tool may further comprise an alignment pin received within the extension, the alignment pin configured to centrally align the pinion gear within the bore of the camshaft.

The ring gear may include a bushing configured to support the camshaft.

The plurality of lugs may project from a rear wall of the ring gear.

The power tool may further comprise a seal disposed about an outer periphery of the ring gear.

The plurality of lugs may project from an outer periphery of the ring gear.

The power tool may further comprise a rib engageable with the first housing portion and the second housing portion to axially secure the ring gear.

The power tool may further comprise a pinion seal coupled to the pinion gear for rotation therewith, wherein the pinion seal is configured to seal an interface between the pinion gear and the camshaft.

The pinion seal may be configured to engage a rear end of the camshaft when the output shaft rotates at a speed less than a threshold speed, and wherein the pinion seal may be configured to disengage from the rear end of the camshaft when the output shaft rotates at a speed greater than the threshold speed.

The threshold speed may be between <NUM>,<NUM> RPM and <NUM>,<NUM> RPM.

The power tool may have an overall length measured along the axis from a rear end of the housing to a front end of the anvil between <NUM> and <NUM>, wherein the power tool may have an overall height measured perpendicular to the axis between <NUM> and <NUM>, and wherein the power tool may be capable of delivering at least <NUM> (<NUM> foot-pounds) of fastening torque to a workpiece through the anvil.

The pinion seal may be configured to engage a rear end of the camshaft when the output shaft rotates at a speed less than a threshold speed, and wherein the pinion seal may be configured to disengage from the rear end of the camshaft when the output shaft rotates at a speed greater than the threshold speed, and wherein the threshold speed corresponds with a no-load speed of the motor.

Other features and aspects of the disclosure will become apparent by consideration of the following detailed description and accompanying drawings.

The present disclosure provides, among other things, embodiments of an impact wrench including combinations of components and dimensions that provide the impact wrench with a very compact overall size but still enable the impact wrench to deliver a large amount of torque to a desired fastening application. For example, in some embodiments, the impact wrench includes a ring gear with a circumferential projection, and the ring gear is directly supported by a clamshell housing of the impact wrench without requiring any additional supports in front of the ring gear. This advantageously reduces the length required for supporting the ring gear. In some embodiments, the impact wrench includes a bearing for supporting a pinion gear coupled to an output shaft of the motor. The bearing is received within a bore of a camshaft at a location in front of the ring gear and associated planet gears. This arrangement also contributes to length reduction. In some embodiments, the impact wrench may include a vibration isolating connection incorporated into a handle of the impact wrench, to reduce the transmission of vibration to a battery pack supported on the handle.

<FIG> illustrates an embodiment of a power tool in the form of a rotary impact tool, and, more specifically, an impact wrench <NUM>. The impact wrench <NUM> includes a housing <NUM> with a motor housing portion <NUM>, an impact case or front housing portion <NUM> coupled to the motor housing portion <NUM> (e.g., by a plurality of fasteners <NUM>), and a handle portion <NUM> extending downwardly from the motor housing portion <NUM>. In the illustrated embodiment, the handle portion <NUM> and the motor housing portion <NUM> are defined by a first clamshell half 28a and a cooperating second clamshell half 28b (i.e., a first housing portion and a second housing portion).

The illustrated housing <NUM> also includes an end cap <NUM> coupled to the motor housing portion <NUM> opposite the front housing portion <NUM>. The first and second housing portions 28a, 28b can be coupled (e.g., fastened) together at an interface or seam <NUM>. In the illustrated embodiment, the end cap <NUM> is continuous and may be pressed or fitted over a rear end of the clamshell halves 28a, 28b. In other words, the end cap <NUM> may not include two halves such that the end cap <NUM> may extend over the seam <NUM>. The end cap <NUM> is coupled to the motor housing portion <NUM> by a plurality of fasteners <NUM> (<FIG>). In yet other embodiments, the impact wrench <NUM> may not include a separate end cap, such that the clamshell halves 28a, 28b instead define the rear end of the motor housing portion <NUM>.

Referring to <FIG> and <FIG>, the impact wrench <NUM> includes a battery <NUM> removably coupled to a battery receptacle <NUM>, which in the illustrated embodiment, includes a cavity extending into the handle portion <NUM>. A motor <NUM> is supported within the motor housing portion <NUM> and receives power from the battery <NUM> via connections, pads, and/or battery terminals <NUM> in the battery receptacle <NUM> when the battery <NUM> is coupled to the battery receptacle <NUM>. In the illustrated embodiment, the handle portion <NUM> of the clamshell halves 28a, 28b can be covered or surrounded by a grip portion <NUM>, which may be overmolded on the handle portion <NUM>.

The battery <NUM> may be a power tool battery pack generally used to supply power to a power tool, such as an electric drill, an electric saw, and the like (e.g., a <NUM> volt rechargeable battery pack, such as an M12 REDLITHIUM battery pack sold by Milwaukee Electric Tool Corporation). The battery <NUM> may include lithium ion (Li-ion) cells. The <NUM> volt nominal output voltage of the battery <NUM> provides an optimal balance between weight/size and power in the illustrated impact wrench <NUM>; however, batteries with other nominal voltages may be used in other embodiments.

Referring to <FIG>, in the illustrated embodiment, the handle portion <NUM> includes an upper portion 26a extending from the motor housing portion <NUM> and a lower portion 26b movably coupled to the upper portion 26a via a vibration isolating connection 26c. The vibration isolating connection 26c includes a damping element <NUM>, which may be made of a vibration damping material, such as an elastomeric material. In some embodiments, the damping element <NUM> may be generally ring-shaped. In the illustrated embodiment, the damping element <NUM> is received in a gap between the upper and lower portions 26a, 26b and covered by the overmolded grip portion <NUM>. In yet other embodiments, the damping element <NUM> may be integrally formed as a single piece with the overmolded grip portion <NUM> (i.e. during the grip overmolding process).

The damping element <NUM> at least partially mechanically isolates the lower portion 26b of the handle portion <NUM> from the upper portion 26a and thereby inhibits transmission of vibration from the upper portion 26a to the lower portion 26b. The battery <NUM> is coupled to and supported by the lower portion 26b. As such, the vibration isolating connection 26c, including the damping element <NUM>, is configured to isolate the battery <NUM> from vibrations produced during operation of the impact wrench <NUM>.

Now referring to <FIG> and <FIG>, in the illustrated embodiment, the motor <NUM> is a brushless direct current ("BLDC") motor with a stator <NUM> and a rotor with an output shaft <NUM> that is rotatable about an axis <NUM> relative to the stator <NUM>. The brushless motor <NUM> preferably has a nominal diameter of <NUM> millimeters, or more than <NUM> millimeters in other embodiments. In yet other embodiments, other types of motors may be used. A fan <NUM> is coupled to the output shaft <NUM> behind the motor <NUM> to generate airflow. The impact wrench <NUM> also includes a switch <NUM> (e.g., a trigger switch; <FIG>) supported by the housing <NUM> that selectively connects the motor <NUM> (e.g., via suitable control circuitry provided on one or more printed circuit board assemblies ("PCBAs") and the battery <NUM> electrically, to provide DC power to the motor <NUM>. In other embodiments, the impact wrench <NUM> may include a power cord for electrically connecting the switch <NUM> and the motor <NUM> to a source of AC power. As a further alternative, the impact wrench <NUM> may be configured to operate using a different power source (e.g., a pneumatic or hydraulic power source, etc.).

In the illustrated embodiment, a first PCBA <NUM> is provided adjacent a front end of the motor <NUM> (<FIG>). The illustrated first PCBA <NUM> includes one or more Hall-Effect sensors, which provide feedback for controlling the motor <NUM>. A second PCBA <NUM> is positioned within the handle portion <NUM> (adjacent a top end of the handle portion <NUM>) and generally between the switch <NUM> and the motor <NUM>. The second PCBA <NUM> is in electrical communication with the motor <NUM>, the switch <NUM>, and the battery receptacle <NUM>. In the illustrated embodiment, the second PCBA <NUM> includes a plurality of semi-conductor switching elements (e.g., MOSFETs, IGBTs, or the like) that control and distribute power to windings in the stator <NUM> in order to cause rotation of the rotor and output shaft <NUM>. The second PCBA <NUM> may also include one or more microprocessors, machine-readable, non-transitory memory elements, and other electrical or electronic elements for providing operational control to the impact wrench <NUM>. In some embodiments, the first PCBA <NUM> may be omitted, and the motor <NUM> may be configured for sensorless control via the second PCBA <NUM>.

In the illustrated embodiment, as best shown in <FIG>, the clamshell halves 28a, 28b are positioned to at least partially overlap one another at the seam <NUM>, and the grip portion <NUM> is shaped to surround the mated clamshell halves 28a, 28b. Fasteners (e.g., fasteners <NUM>) may be threaded, pinned, inserted, etc. into each of the clamshell halves 28a, 28b to further secure the housing <NUM> of the handle portion <NUM> in a closed or generally sealed position.

Referring now to <FIG> and <FIG>, the impact wrench <NUM> further includes a gear assembly <NUM> driven by the output shaft <NUM> and an impact mechanism <NUM> coupled to an output of the gear assembly <NUM>. The impact mechanism <NUM> may also be referred to herein as a drive assembly <NUM>. The gear assembly <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 drive assembly <NUM>. The gear assembly <NUM> is at least partially housed within the housing <NUM>, and specifically within a gear housing portion <NUM> of the housing defined by the clamshell halves 28a, 28b in the illustrated embodiment. That is, the impact wrench <NUM> does not include a separate gear case positioned within the housing <NUM> for supporting the gear assembly <NUM>. Instead, the gear assembly <NUM>-and particularly a ring gear <NUM> of the gear assembly <NUM>-is directly supported by the clamshell halves 28a, 28b. This may advantageously reduce the size, weight, and/or manufacturing cost associated with the impact wrench <NUM>. However, in alternate embodiments, the ring gear <NUM> may be supported within a separate gear case within the housing <NUM>.

In the illustrated embodiment, the motor housing <NUM> and handle portion <NUM> include a rigid polymer or plastic material and the front housing portion <NUM> is metal. In some embodiments, the gear housing portion <NUM> may include additional and/or differently composed material (e.g., stronger) to support the gear assembly <NUM>. As will be described in greater detail below, the configurations of the gear assembly <NUM> and gear housing portion <NUM> of the impact wrench <NUM> described herein advantageously reduces an overall size of the impact wrench <NUM>.

Referring to <FIG>, the gear housing portion <NUM> may contain lubricant, such as grease or oil, that assists in smooth operation of the impact wrench <NUM> by minimizing friction between movable components. The impact wrench <NUM> includes a plurality of sealing elements 75a, 75b, 75c, which inhibit the lubricant from leaking out of the gear housing portion <NUM>. In the illustrated embodiment, first and second elongated sealing elements 75a, 75b are positioned within walls of the clamshell halves 28a, 28b such that the elongated sealing elements 75a, 75b generally extend along and seal upper and lower sides of the gear housing portoin <NUM>. A third sealing element 75c, which is an annular sealing element such as an o-ring, forms a seal between the clamshell halves 28a, 28b and the front housing portion <NUM>.

As illustrated in <FIG> and <FIG>, the gear assembly <NUM> includes a pinion gear <NUM> coupled to the output shaft <NUM> of the motor <NUM>, a plurality of planet gears <NUM> meshed with the pinion gear <NUM>, and a ring gear <NUM> meshed with the planet gears <NUM> and rotationally fixed within the housing <NUM> (specifically, within the gear housing portion <NUM>). A rearward facing side of the ring gear <NUM> is seated against a dividing wall <NUM> formed by the clamshell halves 28a, 28b (<FIG>). The dividing wall <NUM> separates the interior of the gear housing portion <NUM> from the motor <NUM>. The illustrated pinion gear <NUM> includes a recess <NUM> that receives the output shaft <NUM> and an extension <NUM>. The output shaft <NUM> may be press fit into the recess <NUM>, or the output shaft <NUM> and the recess <NUM> may include cooperating spline patterns or other suitable geometries for coupling the pinion gear <NUM> for co-rotation with the output shaft <NUM>. In other embodiments, the pinion gear <NUM> may be integrally formed as a single piece with the output shaft <NUM>.

Referring to <FIG>, the illustrated ring gear <NUM> includes a plurality of lugs <NUM>. In the illustrated embodiment, the lugs <NUM> of the ring gear <NUM> fit within grooves <NUM> formed by the clamshell halves 28a, 28b to support and constrain the ring gear <NUM> in a rotational direction. As shown in <FIG>, the lugs <NUM> include a first set of lugs 170a and a second set of lugs 170b extending from opposite lateral sides of the ring gear <NUM>. The lugs <NUM> are positioned such that the first set of lugs 170a is received by grooves <NUM> of the first clamshell half 28a, and the second set of lugs 170b is received by grooves <NUM> of the second clamshell half 28b. The illustrated ring gear <NUM> includes upper and lower regions <NUM>, <NUM> without any lugs <NUM>. Each of the upper and lower regions <NUM>, <NUM> may span between about <NUM> degrees and about <NUM> degrees of the circumference of the ring gear <NUM>. Because the lugs <NUM> are positioned only along the lateral sides of the ring gear <NUM>, reaction forces experienced by the housing <NUM> due to torque on the ring gear <NUM> during operation of the impact wrench <NUM> have resultant force vectors oriented in a generally vertical direction (i.e., generally parallel to the parting plane of the clamshell halves 28a, 28b. ) For example, the lugs <NUM> may transmit reaction forces with resultant force vectors oriented at angles between <NUM> and <NUM> degrees relative to the parting plane in some embodiments. In some embodiments, the lugs <NUM> may transmit reaction forces with resultant force vectors oriented at angles between <NUM> and <NUM> degrees relative to the parting plane. This reduces separation of the clamshell halves 28a, 28b due the reaction forces.

With reference to <FIG>, the planet gears <NUM> are coupled, via pins <NUM>, to a camshaft <NUM> of the drive assembly <NUM> such that the camshaft <NUM> acts as a planet carrier. Accordingly, rotation of the output shaft <NUM> rotates the planet gears <NUM>, which then advance along the inner circumference of the ring gear <NUM> and thereby rotates the camshaft <NUM>. In the illustrated embodiment, the camshaft <NUM> includes a bore <NUM> extending partially through the camshaft <NUM> along the axis <NUM>. The bore <NUM> is shaped to accommodate and/or receive at least a portion of the pinion gear <NUM>. In the illustrated embodiment, the bore <NUM> extends only partially through the length of the camshaft <NUM>; however, the bore <NUM> may extend through the entire length of the camshaft <NUM>, to reduce the weight of the camshaft <NUM>, in other embodiments.

With reference to <FIG>, the ring gear <NUM> of the impact wrench <NUM> includes a rib <NUM> extending around a circumference of the ring gear <NUM>. The gear housing portion <NUM> includes a recess <NUM> (<FIG>) disposed around an interior circumference of the gear housing portion <NUM>. The rib <NUM> of the ring gear <NUM> is disposed within the recess <NUM> of the gear housing portion <NUM> such that the ring gear <NUM> is axially constrained with respect to the gear housing portion <NUM>. By axially constraining the ring gear <NUM> with a feature along a circumference of the ring gear <NUM>, an overall length OL (<FIG>) of the impact wrench <NUM> is reduced compared to typical impact-type power tools, in which the ring gear may be axially secured using a mechanism that is disposed past a front face of the ring gear (i.e., axially toward the anvil). In such typical impact-type power tools, such securing features may reduce the available space to accommodate rearward travel of the hammer, thus requiring an increase in the overall tool length to accommodate hammer travel.

Referring to <FIG> and <FIG>, the output shaft <NUM> is rotatably supported by a first or forward bearing <NUM> and a second or rear bearing <NUM>. The pinion gear <NUM>, coupled to the output shaft <NUM>, extends through an opening in the dividing wall <NUM>. The impact wrench <NUM> includes a hub or bearing retainer <NUM>, which may be at least partially integrally formed with the end cap <NUM> in some embodiments, and which secures the rear bearing <NUM> both axially (e.g., against forces transmitted along the axis <NUM>) and radially (i.e., against forces transmitted in a radial direction of the output shaft <NUM>). In the illustrated embodiment, the fan <NUM> includes a recess <NUM> and the bearing retainer <NUM> extends into the recess <NUM> such that at least a portion of the bearing retainer <NUM> and at least a portion of the rear bearing <NUM> overlap the fan <NUM> along the axis <NUM> (<FIG>). This overlapping arrangement advantageously reduces the axial length of the impact wrench <NUM>.

With continued reference to <FIG> and <FIG>, the forward bearing <NUM> is axially recessed within the bore <NUM> of the camshaft <NUM> and supports the extension <NUM> of the pinion gear <NUM>. An alignment pin <NUM> is axially recessed within the extension <NUM> and is configured to align the pinion gear <NUM> with the bore <NUM> of the camshaft <NUM> and the forward bearing <NUM> (e.g., during assembly of the impact wrench <NUM>). The forward bearing <NUM> is coupled to and supported by the camshaft <NUM> (e.g., at an outer race of the forward bearing <NUM>), such that at least a portion of the forward bearing <NUM> is located axially in front of ring gear <NUM> and the planet gears <NUM>, and the forward bearing <NUM> is axially aligned with a portion of a spring <NUM>, described in greater detail below. In this manner, the housing <NUM>, spring <NUM>, camshaft <NUM>, forward bearing <NUM>, and the extension <NUM> of the pinion gear <NUM> each overlap along the axis <NUM>. In other words, at least one plane LL (<FIG>) can be drawn in a radially outward direction from the extension <NUM> of the pinion gear <NUM> that intersects the housing <NUM>, spring <NUM>, camshaft <NUM>, and forward bearing <NUM>.

The drive assembly <NUM> of the impact wrench <NUM> will now be described with reference to <FIG>. The drive assembly <NUM> includes an anvil <NUM>, extending from the front housing portion <NUM>, to which a tool element (e.g., a socket, not shown) can be coupled for performing work on a workpiece (e.g., a fastener). The drive assembly <NUM> is configured to convert the constant rotational force or torque provided by the gear assembly <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 wrench <NUM>, the drive assembly <NUM> includes the camshaft <NUM>, a hammer <NUM> supported on and axially slidable relative to the camshaft <NUM>, and the anvil <NUM>. Stated another way, the hammer <NUM> is configured to reciprocate axially along the camshaft <NUM> and impart periodic rotational impacts to the anvil <NUM> in response to rotation of the camshaft <NUM>.

The drive assembly <NUM> further includes a spring <NUM> that biases the hammer <NUM> toward the front of the impact wrench <NUM>. In other words, the 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 spring <NUM> and the hammer <NUM>. The thrust bearing <NUM> and the thrust washer <NUM> allow for the spring <NUM> and the camshaft <NUM> to continue to rotate relative to the hammer <NUM> after each impact strike when lugs <NUM> on the hammer <NUM> engage with corresponding anvil lugs (not shown) and rotation of the hammer <NUM> momentarily stops or reverses. The camshaft <NUM> includes cam grooves <NUM> in which corresponding cam balls <NUM> are received. The cam balls <NUM> are in driving engagement with the hammer <NUM> and 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 are engaged and the camshaft <NUM> continues to rotate. The axial movement of the hammer <NUM> compresses the spring <NUM>, which then releases its stored energy to propel the hammer <NUM> forward and rotate the hammer <NUM> once the hammer lugs <NUM> clear the anvil lugs.

In some embodiments, the hammer spring <NUM> is formed from a cylindrical coil and, therefore, possesses a circular cross-section. In other embodiments, such as the illustrated embodiment, the spring <NUM> of the impact wrench <NUM> is formed from a rectangular coil and possesses a rectangular cross-section. In some embodiments, the cross-section of the spring <NUM> may be square. Because a spring formed with a rectangular or square cross-section has a larger cross-sectional area and larger area moment of inertia than a typical coil spring formed with a circular cross-section having an outer diameter equal to a shortest side length of the rectangular or square-cross-section, the spring <NUM> of the impact wrench <NUM> may have a larger spring constant than a circular coil spring in a typical impact-type power tool with the same outer diameter and number of active coils. Accordingly, the impact wrench <NUM> can be built with smaller dimensions than a typical impact-type power tool while storing an equal or greater amount of hammer energy in the spring <NUM> and thereby providing an equal or larger operating torque. In some embodiments, the spring <NUM> is made from a chrome silicone spring steel.

In the illustrated embodiment, with reference to <FIG> and <FIG>, the impact wrench <NUM> further includes a bushing <NUM> supported by the dividing wall <NUM> and surrounding the camshaft <NUM>. The illustrated bushing <NUM> includes a plurality of arms <NUM> (<FIG>). The arms <NUM> of the bushing <NUM> fit within grooves (not shown) of the housing <NUM> to rotationally fix the bushing <NUM> relative to the housing <NUM>. In some embodiments, the bushing <NUM> may include two arms <NUM> positioned opposite one another to support the bushing <NUM> within the housing <NUM>. A second end of the camshaft <NUM> is supported by the anvil <NUM>, which is retained in the front housing portion <NUM> by an anvil bushing <NUM>.

Referring now to <FIG>, dimensions of the impact wrench <NUM>, according to one example construction, include a first length L1 defined axially between an end of the end cap <NUM> and an end of the trigger switch <NUM>. In the illustrated embodiment, the first length L1 may be between approximately <NUM> and approximately <NUM> (e.g., <NUM>).

The impact wrench <NUM> may include a second length L2 defined axially between the end of the trigger switch <NUM> and a tip of the anvil <NUM>. In the illustrated embodiment, the second length L2 may be between approximately <NUM> and approximately <NUM> (e.g., <NUM>).

The impact wrench <NUM> may further include a third length L3 defined axially between the tip of the anvil <NUM> and a first or rear end of the ring gear <NUM>. In the illustrated embodiment, the third length L3 may be between approximately <NUM> and approximately <NUM> (e.g.,<NUM>).

The impact wrench <NUM> may further include a fourth length L4 defined axially between a rear end of the rear bearing <NUM> and a rear end of forward bearing <NUM>. In the illustrated embodiment, the fourth length L4 may be between approximately <NUM> and approximately <NUM> (e.g., <NUM>).

The impact wrench <NUM> may also include a height H3 defined linearly between a center of a plunger of the trigger switch <NUM> and a bottom of the handle portion <NUM>. In the illustrated embodiment, the height may be between approximately <NUM> and approximately <NUM> (e.g., <NUM>).

As illustrated in <FIG>, the impact wrench <NUM> may also include a fifth length L5 defined axially between a rear end of the camshaft <NUM> and a rear end of the hammer <NUM> when the spring <NUM> is in an uncompressed or free state/condition. In the illustrated embodiment, the fifth length L5 may be between approximately <NUM> and approximately <NUM> (e.g., <NUM>).

The combined dimensions (e.g., L1, L2, L3, L4, L5, H3, OH) of the illustrated impact wrench <NUM> are not known in the art such that the impact wrench <NUM> has advanced ergonomics without sacrificing operation capabilities (e.g., torque transmission, form factor, and the like).

In some embodiments, as illustrated in <FIG>, an overall length OL of the impact wrench <NUM> may be between approximately <NUM> and approximately <NUM> (e.g., <NUM>), and an overall height OH of the impact wrench <NUM> (not including the battery 34_ may be between approximately <NUM> and approximately <NUM> (e.g., <NUM>). In the illustrated embodiment, the overall height OH is <NUM> times greater than the overall length OL.

The features and dimensions of the impact wrench <NUM>, as described above, allow the impact wrench <NUM> to be both compact and lightweight. The impact wrench <NUM> has a total weight, not including the battery <NUM>, between <NUM>,<NUM> and <NUM> (<NUM> and <NUM> pounds) in some embodiments, or between <NUM>,<NUM> and <NUM> (<NUM> and <NUM> pounds) in some embodiments. Furthermore, the impact wrench <NUM> is capable of delivering at least <NUM> (<NUM> foot-lbs. ) of fastening torque to a workpiece in some embodiments, or at least <NUM> (<NUM> foot-lbs. ) of fastening torque in other embodiments. In some embodiments, the impact wrench <NUM> may be capable of delivering between at least <NUM> (<NUM> foot-lbs. ) and <NUM> (<NUM> foot-lbs. ) of fastening torque per pound of weight.

In operation of the impact wrench <NUM>, an operator depresses the switch <NUM> to activate the motor <NUM>, which continuously drives the gear assembly <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 drive surfaces of hammer lugs <NUM> to engage, respectively, the driven surfaces of anvil lugs to provide an impact and to rotatably drive the anvil <NUM> and the tool element. 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.

As the hammer <NUM> moves rearward, the cam balls <NUM> situated in the respective cam grooves <NUM> in the camshaft <NUM> move rearward in the cam grooves <NUM>. The 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, the hammer <NUM> continues to rotate and moves or slides forwardly, toward the anvil <NUM>, as the spring <NUM> releases its stored energy, until the drive surfaces of the hammer lugs <NUM> re-engage the driven surfaces of the anvil lugs to cause another impact.

<FIG> illustrates a power tool in the form of an impact wrench <NUM> according to another embodiment. The impact wrench <NUM> is similar in some aspects to the impact wrench <NUM> described above with reference to <FIG>, and features of the impact wrench <NUM> corresponding with features of the impact wrench <NUM> are given corresponding reference numerals plus '<NUM>. ' The following description focuses primarily on differences between the impact wrench <NUM> and the impact wrench <NUM>, and it should be understood that features of the impact wrench <NUM> and alternatives described herein may be incorporated into the impact wrench <NUM> where applicable, and vice versa.

Referring to <FIG>, the illustrated impact wrench <NUM> includes a housing <NUM> with a motor housing portion <NUM>, an impact case or front housing portion <NUM> coupled to the motor housing portion <NUM>, and a handle portion <NUM> extending from the motor housing portion <NUM>. The handle portion <NUM> and the motor housing portion <NUM> are defined by a first clamshell half 228a and a cooperating second clamshell half 228b, coupled together at an interface or seam <NUM>.

With reference to <FIG>, a motor <NUM> (e.g., a BLDC motor) is supported within the motor housing portion <NUM> and includes a stator <NUM> and a rotor with an output shaft <NUM> that is rotatable about an axis <NUM> relative to the stator <NUM>. The impact wrench <NUM> also includes a switch <NUM> (e.g., a trigger switch; <FIG>) supported by the housing <NUM> that selectively connects the motor <NUM> (e.g., via suitable control circuitry provided on one or more printed circuit board assemblies ("PCBAs") and a battery (not shown) electrically, to provide DC power to the motor <NUM>.

A first PCBA <NUM> is provided adjacent a front end of the motor <NUM>. The illustrated first PCBA <NUM> includes one or more Hall-Effect sensors, which provide feedback for controlling the motor <NUM>. A second PCBA <NUM> is positioned within the handle portion <NUM> (adjacent a top end of the handle portion <NUM>) and generally between the switch <NUM> and the motor <NUM>. The second PCBA <NUM> is in electrical communication with the motor <NUM>, the switch <NUM>, and terminals of a battery receptacle <NUM> located in the handle portion <NUM>. In the illustrated embodiment, the second PCBA <NUM> includes a plurality of semi-conductor switching elements (e.g., MOSFETs, IGBTs, or the like) that control and distribute power to windings in the stator <NUM> in order to cause rotation of the rotor and output shaft <NUM>. The second PCBA <NUM> may also include one or more microprocessors, machine-readable, non-transitory memory elements, and other electrical or electronic elements for providing operational control to the impact wrench <NUM>. In some embodiments, the first PCBA <NUM> may be omitted, and the motor <NUM> may be configured for sensorless control via the second PCBA <NUM>.

The impact wrench <NUM> includes a gear assembly <NUM> driven by the output shaft <NUM> and an impact mechanism or drive assembly <NUM> coupled to an output of the gear assembly <NUM>. The gear assembly <NUM> is at least partially housed within a gear housing portion <NUM> that is defined by the clamshell halves 228a, 228b and the front housing portion <NUM>. Thus, like the impact wrench <NUM>, the impact wrench <NUM> does not include a separate gear case positioned within the housing <NUM> for supporting the gear assembly <NUM>. Instead, the gear assembly <NUM>-and particularly a ring gear <NUM> of the gear assembly <NUM>-is directly supported by the clamshell halves 228a, 228b. This may allow the ring gear <NUM> to have a larger diameter within a given size of the housing <NUM> than if the ring gear <NUM> were supported within a separate gear case within the housing <NUM>. In the illustrated embodiment, the ring gear <NUM> may have an outer diameter that is greater than an inner diameter of the front housing portion <NUM>.

Like the impact wrench <NUM>, the drive assembly of the impact wrench <NUM> includes a camshaft <NUM>, an anvil <NUM>, a hammer <NUM>, and a hammer spring <NUM>. With reference to <FIG>, the gear assembly <NUM> includes a pinion gear <NUM> coupled to the output shaft <NUM> of the motor <NUM>, a plurality of planet gears <NUM> meshed with the pinion gear <NUM>, and the ring gear <NUM>, which is meshed with the planet gears <NUM> and rotationally fixed within the housing <NUM> (specifically, within the gear housing portion <NUM>). The ring gear <NUM> is positioned within a groove <NUM> bounded in the axial direction by a first wall <NUM>, which may be referred to as a dividing wall, and a second wall <NUM>. The first wall <NUM> and the second wall <NUM> are each collectively defined by the two clamshell halves 228a, 228b. The first wall <NUM> separates the interior of the gear housing portion <NUM> from the motor <NUM>. The second wall <NUM> is generally annular and centered with respect to the rotational axis <NUM>. In the illustrated embodiment, the second wall <NUM> includes a portion of a boss <NUM>, which projects into the gear housing portion <NUM> and receives a screw (not shown) to couple the clamshell halves 228a, 228b together.

As shown in <FIG> and <FIG>, the ring gear <NUM> includes a rear wall <NUM> with lugs 240a, 240b projecting from the rear wall <NUM>. The lugs 240a, 240b are received within correspondingly shaped receptacles <NUM> in the first wall <NUM> to prevent rotation of the ring gear <NUM> relative to the housing <NUM>. In the illustrated embodiment, the lugs 240a, 240b are generally linear and extend in a lateral (i.e., horizontal) direction perpendicular to the axis <NUM> and offset above and below the axis <NUM>. The lugs 240a, 240b are interconnected by arcuate webs 240c surrounding an aperture <NUM> extending through the rear wall <NUM> of the ring gear <NUM>. In some embodiments, the ring gear <NUM>, including the lugs 240a, 240b and webs 240c may be integrally formed as a single piece from powdered metal. In other embodiments, the ring gear <NUM> may be formed in other ways.

Because the lugs 240a, 240b and the receptacles <NUM> are horizontally oriented, reaction forces on the first wall <NUM> of the housing <NUM> due to torque on the ring gear <NUM> during operation of the impact wrench <NUM> have resultant force vectors that are oriented in a generally vertical direction (i.e. generally parallel to the parting plane of the clamshell halves 228a, 228b. ) For example, the lugs 240a, 240b may transmit reaction forces with resultant force vectors oriented at angles between <NUM> and <NUM> degrees relative to the parting plane in some embodiments or at angles between <NUM> and <NUM> degrees relative to the parting plane in some embodiments. The resultant force vectors therefore do not tend to cause separation of the clamshell halves 228a, 228b. This maintains the stability of the ring gear <NUM> and inhibits lubricant from leaking out of the gear housing portion <NUM>.

Referring to <FIG>, the ring gear <NUM> includes an integrated bushing <NUM> defining the aperture <NUM> and rotationally supporting a rear end of the camshaft <NUM>. The lugs 240a, 240b, webs 240c, and rear wall <NUM> together define a thickness of the bushing <NUM>. In other embodiments, the rear end of the camshaft <NUM> may be supported in other ways, such as by a bearing supported within the aperture <NUM>.

Best illustrated in <FIG>, the ring gear <NUM> includes a radial groove <NUM> on the exterior of the ring gear <NUM>, which receives a sealing member <NUM> (i.e., an O-ring). The O-ring <NUM> serves to inhibit lubrication from the gear housing portion <NUM> from leaking into the motor housing portion <NUM>.

The illustrated pinion gear <NUM> includes a recess <NUM> that receives the output shaft <NUM> and an extension <NUM>. The output shaft <NUM> may be press fit into the recess <NUM>, or the output shaft <NUM> and the recess <NUM> may include cooperating spline patterns or other suitable geometries for coupling the pinion gear <NUM> for co-rotation with the output shaft <NUM>. In other embodiments, the pinion gear <NUM> may be integrally formed as a single piece with the output shaft <NUM>.

As shown in <FIG>, the impact wrench <NUM> further includes a pinion seal <NUM>, which in the illustrated embodiment is configured as a V-ring with a resilient flange <NUM> engageable with rear surfaces of the camshaft <NUM> and/or ring gear <NUM>. The pinion seal <NUM> may be made of a flexible, resilient material, such as an elastomeric material in some embodiments. The illustrated pinion seal <NUM> is coupled to the pinion gear <NUM> (e.g., via an interference fit) for co-rotation therewith. In some embodiments, the inner periphery of the pinion seal <NUM> and the outer periphery of the pinion gear <NUM> may include cooperating non-circular geometries to couple the pinion seal <NUM> for co-rotation with the pinion gear <NUM>. In the illustrated embodiment, the pinion gear <NUM> includes a shoulder <NUM> formed adjacent an end of the pinion gear <NUM> opposite the extension <NUM>. The shoulder <NUM> may act as a back stop to prevent axial displacement of the pinion seal <NUM>.

The flange <NUM> is configured to cover and thereby seal a camshaft-pinion interface <NUM> defined between an outer surface of the pinion gear <NUM> and an inner surface of the camshaft <NUM>. Because the pinion gear <NUM> rotates at a different speed than the camshaft <NUM>, a small clearance exists along the camshaft-pinion interface <NUM>. The flange <NUM> of the pinion seal <NUM> inhibits lubricant from migrating into the motor housing portion <NUM> through the camshaft-pinion interface <NUM>. In some embodiments, the flange <NUM> may also be configured to cover and thereby seal a camshaft-ring gear interface <NUM> defined between an outer surface of the camshaft <NUM> and an inner surface of the bushing <NUM> of the ring gear <NUM>. The flange <NUM> of the pinion seal <NUM> may therefore also inhibit lubricant from migrating into the motor housing portion <NUM> through the camshaft-ring gear interface <NUM>.

The flange <NUM> extends at an oblique angle relative to the axis <NUM>; however, the angle may vary depending on the rotational speed of the motor shaft <NUM> and pinion gear <NUM>. In particular, the angle may increase toward <NUM> degrees when the rotational speed of the motor shaft <NUM> exceeds a threshold speed, due to centrifugal forces on the flange <NUM> deforming the resilient material. The threshold speed may correspond with a no-load or idle speed of the motor <NUM>, during which the hammer <NUM> does not reciprocate and impart impacts to the anvil <NUM>. In some embodiments, the threshold speed is <NUM>,<NUM> RPM. In some embodiments, the threshold speed is <NUM>,<NUM> RPM. In some embodiments, the threshold speed is between <NUM>,<NUM> RPM and <NUM>,<NUM> RPM.

When the flange <NUM> deforms to increase the angle above the threshold speed, the flange <NUM> moves away from and out of engagement from the rear end of the camshaft <NUM> and the rear end of the ring gear <NUM>. This advantageously reduces friction and wear that could otherwise occur at such high rotational speeds. Furthermore, the inventors have found that lubricant migration along the camshaft-pinion interface <NUM> and the camshaft-ring gear interface <NUM> is minimal at speeds above the threshold speed, since, during idle, the hammer <NUM> does not reciprocate.

Once load is applied to the motor <NUM> (e.g., when the anvil <NUM> engages a fastener offering sufficient resistance), the motor <NUM> slows the motor shaft <NUM> to a speed below the threshold speed. The flange <NUM> resiliently recovers to re-engage with the rear end of the camshaft <NUM> and/or the rear end of the ring gear <NUM>. When the hammer <NUM> proceeds to reciprocate during a fastening operation, which may act like a piston to displace the lubricant, cause localized pressure increases, as well increase the temperature of the lubricant, the pinion seal <NUM> inhibits the lubricant from entering the motor housing portion <NUM> via the interfaces <NUM>, <NUM>.

In other embodiments, the seal <NUM> may be constructed in other ways and from other materials. For example, in some embodiments, the seal <NUM> may be a radial seal disposed radially between the pinion gear <NUM> and the interior surface of the camshaft <NUM>. In such embodiments, the seal <NUM> may be carried by either the camshaft <NUM> or the pinion gear <NUM>. In some embodiments, the seal <NUM> may include polyurethane. In other embodiments, the seal <NUM> may include a felt washer. In other embodiments, the seal <NUM> may include a multi-layer composition, such as a layer of foam, a layer of metal, and another layer of foam or a layer of elastomer.

Claim 1:
A power tool (<NUM>, <NUM>) comprising:
a housing (<NUM>, <NUM>) having a first housing portion (28a, 228a) and a second housing portion (28b, 228b) coupled to the first housing portion (28a, 228a);
a motor (<NUM>, <NUM>) directly mounted within the housing (<NUM>, <NUM>) between the first and second housing portions (28a, 28b, 228a, 228b) and including an output shaft (<NUM>, <NUM>), the output shaft (<NUM>, <NUM>) defining an axis (<NUM>, <NUM>);
a gear assembly (<NUM>, <NUM>) supported within the housing (<NUM>, <NUM>) and operably coupled to the motor (<NUM>, <NUM>), the gear assembly (<NUM>, <NUM>) including a ring gear (<NUM>, <NUM>) directly supported by the first and second housing portions (28a, 28b, 228a, 228b), a pinion gear (<NUM>, <NUM>) coupled for co-rotation with the output shaft (<NUM>, <NUM>), and a plurality of planet gears (<NUM>, <NUM>) meshed with the pinion gear (<NUM>, <NUM>) and the ring gear (<NUM>, <NUM>); and
a drive assembly (<NUM>, <NUM>) operably coupled to the gear assembly (<NUM>, <NUM>), the drive assembly (<NUM>, <NUM>) including a camshaft (<NUM>, <NUM>), an anvil (<NUM>, <NUM>), a hammer (<NUM>, <NUM>) configured to reciprocate along the camshaft (<NUM>, <NUM>) to impart rotational impacts to the anvil (<NUM>, <NUM>) in response to rotation of the camshaft (<NUM>, <NUM>), and a spring (<NUM>, <NUM>) biasing the hammer (<NUM>, <NUM>) towards the anvil (<NUM>, <NUM>),
characterized in that
the ring gear (<NUM>, <NUM>) includes a plurality of lugs (<NUM>, <NUM>, 240b) engaged with the first housing portion (28a, 228a) and the second housing portion (28b, 228b) to rotationally constrain the ring gear (<NUM>, <NUM>).