Patent Description:
The present invention relates to rotary power tools, and more particularly to rotary power tools with reciprocating spindles.

Some power tools include a spindle that reciprocates while rotating in a housing. The spindle is sometimes supported by a bearing that moves along the housing as the spindle reciprocates.

<CIT> relates to a hand-held power too. According to the abstract of this document, there is disclosed a hand-held power tool having a housing and a tool holder, which is disposed on a drive shaft that is rotationally mounted in at least one first and one second ball bearing, the first ball bearing having a first inner ring and the second ball bearing having a second inner ring, a spring element is disposed between the first inner ring and the second inner ring in order to pre-stress the first ball bearing with respect to the second ball bearing.

<CIT> relates to an impact drill striker mechanism. According to the abstract of this document, there is provided an impact drill striker mechanism having a striker body guided in the axial direction and acting on the drill spindle. It is thrust by three springs at <NUM> deg. intervals round the periphery, these being periodically compressed and then released. The body is guided on three bolts so that it cannot rotate, the bolts also forming guides for the springs. A recess can be formed in it near the motor spindle driving pinion.

The present invention is defined in appended claim <NUM>. Possible variations are described in the appended dependent claims.

As shown in <FIG>, a rotary power tool, in this embodiment a hammer drill <NUM>, includes a housing <NUM>, a drive mechanism <NUM> and a spindle <NUM> rotatable in response to receiving torque from the drive mechanism <NUM>. As shown in <FIG>, the drive mechanism <NUM> includes an electric motor <NUM> and a multi-speed transmission <NUM> between the motor <NUM> and the spindle <NUM>. The drive mechanism <NUM> is at least partially enclosed by a transmission housing <NUM>. As shown in <FIG> and <FIG>, a chuck <NUM> is provided at the front end of the spindle <NUM> so as to be co-rotatable with the spindle <NUM>. The chuck <NUM> includes a plurality of jaws <NUM> configured to secure a tool bit or a drill bit (not shown), such that when the drive mechanism <NUM> is operated, the bit can perform a rotary and/or percussive action on a fastener or workpiece. The hammer drill <NUM> includes a pistol grip handle <NUM>, a trigger <NUM> for activating the motor <NUM>, and an auxiliary handle <NUM> that can be selectively removed from the transmission housing <NUM>. The hammer drill <NUM> may be powered by an on-board power source such as a battery <NUM> or a remote power source (e.g., an alternating current source) via a cord (not shown).

With reference to <FIG> and <FIG>, the hammer drill <NUM> includes a first ratchet <NUM> coupled for co-rotation with the spindle <NUM> and a second ratchet <NUM> axially and rotationally fixed to the transmission housing <NUM>. In other embodiments, the second ratchet <NUM> is rotationally fixed, but axially moveable relative to the transmission housing <NUM>. As shown in <FIG>, <FIG> and <FIG>, a first bearing <NUM> with an outer race <NUM> having an edge <NUM> is radially positioned between the transmission housing <NUM> and the spindle <NUM> and supports a front portion <NUM> of the spindle <NUM>. In the illustrated embodiment, the edge <NUM> is chamfered, but in other embodiments, the chamfered edge <NUM> is a part separate from the outer race <NUM>.

Although not shown, the second ratchet <NUM> may include a bearing pocket defined in a rear end of the second ratchet <NUM>. A second bearing <NUM> may be at least partially positioned in the bearing pocket and may support a rear portion <NUM> of the spindle <NUM>. The second bearing <NUM> may be wholly received in the bearing pocket, and in other embodiments the second bearing <NUM> may at least partially extend from the bearing pocket. By incorporating the bearing pocket in the second ratchet <NUM>, the second bearing <NUM> may be arranged about the rear portion <NUM> of the spindle <NUM> in a nested relationship within the second ratchet <NUM>, thereby reducing the overall length of the hammer drill <NUM> while also supporting rotation of the spindle <NUM>.

With reference to <FIG>, the hammer drill <NUM> includes a collar <NUM> that is rotatably adjustable by an operator of the hammer drill <NUM> to shift between "hammer drill," "drill-only," and "screwdriver" modes of operation, and to select a particular clutch setting when in "screwdriver mode. " Thus, the collar <NUM> is conveniently provided as a single collar that can be rotated to select different operating modes of the hammer drill <NUM> and different clutch settings. As shown in <FIG> and <FIG>, the hammer drill <NUM> also includes an electronic clutch <NUM> capable of limiting the amount of torque that is transferred from the spindle <NUM> to a fastener (i.e., when in "screwdriver mode") by deactivating the motor <NUM> in response to a detected torque threshold or limit. The electronic clutch <NUM> includes a printed circuit board ("PCB") <NUM> coupled to the transmission housing <NUM> and a wiper (not shown), which is coupled for co-rotation with the collar <NUM>. The PCB <NUM> includes a plurality of electrical pads <NUM> which correspond to different clutch settings of the hammer drill <NUM>.

The hammer drill <NUM> also includes a hammer lockout mechanism <NUM> (<FIG>) for selectively inhibiting the first and second ratchets <NUM>, <NUM> from engaging when the hammer drill <NUM> is in a "screwdriver mode" or a "drill-only mode. " The hammer lockout mechanism <NUM> includes a selector ring <NUM> coupled for co-rotation with and positioned inside the collar <NUM>, and a plurality of balls <NUM> situated within corresponding radial apertures A1, A2, A3, A4, and A5 asymmetrically positioned around and extending through an annular portion <NUM> of the transmission housing <NUM>.

As shown in <FIG>, <FIG>, and <FIG>, but not shown in <FIG>, a sleeve bushing <NUM> is positioned on an inner surface <NUM> of the annular portion <NUM>. The bushing <NUM> can be formed or secured along the inner surface <NUM> of the annular portion <NUM> in a variety of ways, including but not limited to insert molding, pressing, shrink fitting, or trapping with a retaining ring or screws. The annular portion <NUM> of the transmission housing <NUM> is formed of a relatively soft material including but not limited to aluminum or magnesium, whereas the bushing <NUM> is formed of a relatively harder material than aluminum or magnesium, including but not limited to steel. In some embodiments, the relatively softer material is below <NUM> HRC and the relatively harder material is equal to or above <NUM> HRC. In other embodiments, the relatively softer material is less is below <NUM> HRC and the relatively harder material is equal to or above <NUM> HRC.

In the illustrated embodiment, the bushing <NUM> is located along the length of the inner surface <NUM> of the annular portion <NUM>, which includes a plurality of radially inward-extending protrusions P1-P5 extending through sleeve bushing <NUM>. The apertures A1-A5 respectively extend through the protrusions P1-PS of the annular portion <NUM>, such that the apertures A1-A5 are defined by the softer material forming the protrusions P1-P5 and the rest of annular portion <NUM>. Specifically, the apertures A1-AS extend from an inner end of the protrusions P1-P5 to an outer surface of the annular portion <NUM>. In other embodiments, the protrusions P1-P5 are omitted and the apertures A1-A5 are at least partially defined by the sleeve bushing <NUM>. In other embodiments, the protrusions P1-P5 are omitted and the bushing <NUM> can be located in front of the apertures A1-AS (i.e., with the chuck <NUM> located at the front of the hammer drill <NUM>), such that no portion of the bushing <NUM> intersects or overlaps the apertures A1-A5, as shown in <FIG>. In some embodiments, the bushing <NUM> may extend forward along the inner surface <NUM> toward a distal end <NUM> of the annular portion <NUM>, as shown in <FIG>.

In the illustrated embodiment shown in <FIG> and <FIG>, only the ball <NUM> in aperture A5 is shown, but each of the other apertures A1, A2, A3, and A4 also contains a ball <NUM>. As shown in <FIG>, <FIG> and <FIG>, the selector ring <NUM> includes a plurality of recesses R1, R2, R3, R4, and R5 asymmetrically positioned about an inner periphery <NUM> of the selector ring <NUM>. The number of recesses R1-R5 corresponds to the number of apertures A1-A5 and the number of balls <NUM> within the respective apertures A1-A5.

In the illustrated embodiment, five apertures A1-A5, each containing a ball <NUM>, are located in the transmission housing <NUM> and five recesses R1-R5 are defined in the selector ring <NUM>. However, in other embodiments, the hammer lockout mechanism <NUM> could employ more or fewer apertures, balls, and recesses. As shown in <FIG> and <FIG>, the five apertures A1-A5 are approximately located at <NUM> degrees, <NUM> degrees, <NUM> degrees, <NUM> degrees, and <NUM> degrees, respectively, measured in a counterclockwise direction from an oblique plane <NUM> containing a longitudinal axis <NUM> of the hammer drill <NUM> and bisecting aperture A1. As shown in <FIG> and <FIG>, the first ratchet <NUM> and the first bearing <NUM> are set within a cylindrical cavity <NUM> defined within the annular portion <NUM> of the transmission housing <NUM>, and the selector ring <NUM> is radially arranged between the annular portion <NUM> and the collar <NUM>, surrounding the apertures A1-A5.

In operation, as shown in <FIG> when the collar <NUM> and ring <NUM> are rotated together to a position corresponding to a "hammer drill" mode, all five apertures A1-A5 are aligned with all five recesses R1-R5 in the selector ring <NUM>, respectively. Therefore, when the spindle <NUM> is slid rearward relative to the transmission housing <NUM> in response to contact with a workpiece, the chamfered edge <NUM> of the first bearing <NUM> displaces the balls <NUM> situated in the respective apertures A1-A5 radially outward and partially into the recesses R1-R5, thereby disabling the hammer lockout mechanism <NUM>. Thus, the first ratchet <NUM> is permitted to engage with the second ratchet <NUM> to impart reciprocation to the spindle <NUM> as it rotates.

As the spindle <NUM> reciprocates during "hammer drill" mode, the first bearing <NUM> reciprocates within the cavity <NUM>, causing the outer race <NUM> of the first bearing <NUM> to move along the inner surface <NUM> of the annular portion <NUM>. Because the outer race <NUM> slides along the sleeve bushing <NUM>, which is formed of a harder material than the rest of the annular portion <NUM>, the longevity of the transmission housing <NUM>, and the inner surface <NUM> of the annular portion <NUM> in particular, is increased compared to a transmission housing <NUM> without the sleeve bushing <NUM>. Through testing, it has been found that in absence of the bushing <NUM>, the spindle <NUM> experiences wobble at <NUM>,<NUM> reciprocation cycles of the bearing <NUM>. But, when the bushing <NUM> is used, the spindle <NUM> does not experience wobble even after <NUM>,<NUM> reciprocation cycles of the bearing <NUM>. The sleeve bushing <NUM> wears at a much lower rate than the inner surface <NUM> of the annular portion <NUM>, thus maintaining alignment of the spindle <NUM> with the longitudinal axis <NUM> of the hammer drill <NUM> throughout a longer period of the useful life of the hammer drill <NUM>.

When the collar <NUM> and selector ring <NUM> are incrementally rotated (e.g., by <NUM> degrees) in a counterclockwise direction to the second rotational position shown in <FIG>, none of the apertures A1-A5 are aligned with the recesses R1-R5. Thus, in this position of the collar <NUM> and selector ring <NUM>, the balls <NUM> in the respective apertures A1-A5 are prevented from being radially displaced into the recesses R1-R5 in response to the spindle <NUM> contacting a workpiece (via the chuck <NUM> and an attached drill or tool bit). Rather, the chamfered edge <NUM> of the first bearing <NUM> presses against the balls <NUM>, which in turn abut against the inner periphery <NUM> of the selector ring <NUM> and are inhibited from displacing radially outward. Thus, the spindle <NUM> is prevented from moving rearward, maintaining a gap <NUM> between the first and second ratchets <NUM>, <NUM>. Thus, in the second rotational position of the collar <NUM> and the selector ring <NUM>, the hammer lockout mechanism <NUM> is enabled, preventing the spindle <NUM> from reciprocating in an axial manner as it is rotated by the drive mechanism <NUM>, operating the hammer drill <NUM> in a "drill only" mode.

There are a total of twenty different positions between which the collar <NUM> and selector ring <NUM> can rotate, such that the collar <NUM> is rotated <NUM> degrees between each of the positions. The wiper is in electrical and sliding contact with the PCB <NUM> as the collar <NUM> is rotated between each of the twenty positions. Depending upon which of the electrical pads <NUM> on the PCB <NUM> the wiper contacts, the electronic clutch <NUM> adjusts which clutch setting to apply to the motor <NUM>. In the "hammer drill" mode and the "drill only" mode coinciding with the first and second rotational positions of the collar <NUM> and selector ring <NUM>, respectively, the electronic clutch <NUM> operates the motor <NUM> to output torque at a predetermined maximum value to the spindle <NUM>. In some embodiments, the predetermined maximum value of torque output by the motor <NUM> may coincide with the maximum rated torque of the motor <NUM>.

As shown in <FIG> and the Table below, the "hammer drill" position of the collar <NUM> corresponds to a "<NUM> degree" or "first rotational position" position of the collar <NUM>, in which the recesses R1, R2, R3, R4, R5 of the selector ring <NUM> are respectively and approximately located at <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> degrees counterclockwise from the plane <NUM>, such that the apertures A1, A2, A3, A4, A5 are thereby aligned. When the collar <NUM> is rotated <NUM> degrees counterclockwise from the "hammer drill" position to the "drill only" or "second rotational position" as shown in <FIG>, the recesses R1, R2, R3, R4, R5 are respectively and approximately located at <NUM> degrees, <NUM> degrees, <NUM> degrees, <NUM> degrees, and <NUM> degrees counterclockwise from the plane <NUM>.

As shown in the Table below and in <FIG>, the operator may continue to cycle through eighteen additional rotational positions of the collar <NUM>, each corresponding to a different clutch setting in "screwdriver mode", by incrementally rotating the collar <NUM> counterclockwise by <NUM> degrees each time. The first clutch setting (<FIG>) provides a torque limit that is slightly less than the predetermined maximum value of torque output by the motor <NUM> available in the "hammer drill" mode or the "drill only" mode. As the clutch setting number numerically increases, the torque threshold applied to the motor <NUM> decreases, with the eighteenth clutch setting (shown in <FIG>) providing the lowest torque limit to the motor <NUM>.

As can be seen in <FIG> and <FIG>, and the Table below, the "hammer drill" position in <FIG> is the only position in which all five apertures A1-A5 are aligned with all five recesses R1-R5, thereby disabling the hammer lockout mechanism <NUM> as described above. In every other setting of the collar <NUM> and selector ring <NUM>, no more than two of any of the apertures A1-A5 are aligned with the recesses R1-R5. Therefore, in "drill-only" mode (<FIG>) and "screwdriver mode" (<FIG>, clutch settings <NUM>-<NUM>), at least three balls <NUM> inhibit the rearward movement of the spindle <NUM>, via the first bearing <NUM>, thereby enabling the hammer lockout mechanism <NUM> and preventing axial reciprocation of the spindle <NUM> as it rotates.

To adjust the hammer drill <NUM> between "screwdriver" mode, "drill only" mode, and "hammer drill" mode, the collar <NUM> may be rotated a full <NUM> degrees and beyond in a single rotational direction, clockwise or counterclockwise, without any stops which would otherwise limit the extent to which the collar <NUM> may be rotated. Therefore, if the operator is using the hammer drill <NUM> in "screwdriver mode" on the eighteenth clutch setting (<FIG>), the operator needs only to rotate the collar <NUM> counterclockwise by an additional <NUM> degrees to switch the hammer drill <NUM> into "hammer drill" mode, rather than rotating the collar <NUM> in an opposite (clockwise) direction back through clutch settings <NUM> to l and "drill only" mode.

Claim 1:
A rotary power tool (<NUM>) comprising:
a drive mechanism (<NUM>) including an electric motor (<NUM>) and a transmission (<NUM>);
a housing (<NUM>) enclosing at least a portion of the drive mechanism (<NUM>), the housing (<NUM>) including an annular portion (<NUM>);
a spindle (<NUM>) rotatable in response to receiving torque from the drive mechanism (<NUM>);
a first ratchet (<NUM>) coupled for co-rotation with the spindle (<NUM>);
a second ratchet (<NUM>) rotationally fixed to the housing (<NUM>);
a sleeve bushing (<NUM>) on an inner surface (<NUM>) of the annular portion (<NUM>) of the housing (<NUM>); and
a bearing (<NUM>) arranged between the spindle (<NUM>) and the sleeve bushing (<NUM>) and rotatably supporting the spindle (<NUM>), the bearing (<NUM>) having an outer race (<NUM>),
wherein the spindle (<NUM>) is movable relative to the annular portion (<NUM>) of the housing (<NUM>) in response to contact with a workpiece, causing the first and second ratchets (<NUM>, <NUM>) to engage and the spindle (<NUM>) to reciprocate while rotating,
and wherein the outer race (<NUM>) of the bearing (<NUM>) moves along the sleeve bushing (<NUM>) during reciprocation of the spindle (<NUM>) when the first ratchet (<NUM>) and second ratchet (<NUM>) are engaged, and
characterized in that
the first ratchet (<NUM>) and the bearing (<NUM>) are set within a cylindrical cavity (<NUM>) defined within the annular portion (<NUM>) of the transmission housing (<NUM>).