Patent ID: 12202115

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION

As shown inFIGS.1-3, a rotary power tool, in this embodiment a hammer drill10, includes a housing12, a drive mechanism14and a spindle18rotatable in response to receiving torque from the drive mechanism14. As shown inFIG.3, the drive mechanism14includes an electric motor22and a multi-speed transmission26between the motor22and the spindle18. The drive mechanism14is at least partially enclosed by a transmission housing30. As shown inFIGS.1and3, a chuck34is provided at the front end of the spindle18so as to be co-rotatable with the spindle18. The chuck34includes a plurality of jaws38configured to secure a tool bit or a drill bit (not shown), such that when the drive mechanism14is operated, the bit can perform a rotary and/or percussive action on a fastener or workpiece. The hammer drill10includes a pistol grip handle36, a trigger39for activating the motor22, and an auxiliary handle40that can be selectively removed from the transmission housing30. The hammer drill10may be powered by an on-board power source such as a battery41or a remote power source (e.g., an alternating current source) via a cord (not shown).

With reference toFIGS.2and3, the hammer drill10includes a first ratchet42coupled for co-rotation with the spindle18and a second ratchet46axially and rotationally fixed to the transmission housing30. In other embodiments, the second ratchet46is rotationally fixed, but axially moveable relative to the transmission housing30. As shown inFIGS.3,4and6, a first bearing50with an outer race52having an edge54is radially positioned between the transmission housing30and the spindle18and supports a front portion58of the spindle18. In the illustrated embodiment, the edge54is chamfered, but in other embodiments, In other embodiments, the chamfered edge54is a part separate from the outer race52. In other embodiments, the

As shown inFIG.3, the second ratchet46includes a bearing pocket62defined in a rear end of the second ratchet46. A second bearing66is at least partially positioned in the bearing pocket62and supports a rear portion70of the spindle18. In the illustrated embodiment, the second bearing66is wholly received in the bearing pocket62, but in other embodiments the second bearing66may at least partially extend from the bearing pocket62. By incorporating the bearing pocket62in the second ratchet46, the second bearing66is arranged about the rear portion70of the spindle18in a nested relationship within the second ratchet46, thereby reducing the overall length of the hammer drill10while also supporting rotation of the spindle18.

With reference toFIGS.1-7, the hammer drill10includes a collar74that is rotatably adjustable by an operator of the hammer drill10to shift between “hammer drill,” “drill-only,” and “screwdriver” modes of operation, and to select a particular clutch setting when in “screwdriver mode.” Thus, the collar74is conveniently provided as a single collar that can be rotated to select different operating modes of the hammer drill10and different clutch settings. As shown inFIGS.2and3, the hammer drill10also includes an electronic clutch78capable of limiting the amount of torque that is transferred from the spindle18to a fastener (i.e., when in “screwdriver mode”) by deactivating the motor22in response to a detected torque threshold or limit. The electronic clutch78includes a printed circuit board (“PCB”)82coupled to the transmission housing30and a wiper (not shown), which is coupled for co-rotation with the collar74. The PCB82includes a plurality of electrical pads86which correspond to different clutch settings of the hammer drill10.

The hammer drill10also includes a hammer lockout mechanism90(FIGS.4-7) for selectively inhibiting the first and second ratchets42,46from engaging when the hammer drill10is in a “screwdriver mode” or a “drill-only mode.” The hammer lockout mechanism90includes a selector ring94coupled for co-rotation with and positioned inside the collar74, and a plurality of balls98situated within corresponding radial apertures A1, A2, A3, A4, and A5asymmetrically positioned around and extending through an annular portion102of the transmission housing30.

As shown inFIGS.3,4, and6, but not shown inFIG.2, a sleeve bushing105is positioned on an inner surface103of the annular portion102. The bushing105can be formed or secured along the inner surface103of the annular portion102in a variety of ways, including but not limited to insert molding, pressing, shrink fitting, or trapping with a retaining ring or screws. The annular portion102of the transmission housing30is formed of a relatively soft material including but not limited to aluminum or magnesium, whereas the bushing105is 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 20 HRC and the relatively harder material is equal to or above 20 HRC. In other embodiments, the relatively softer material is less is below 40 HRC and the relatively harder material is equal to or above 40 HRC.

In the illustrated embodiment, the bushing105is located along the length of the inner surface103of the annular portion102, which includes a plurality of radially inward-extending protrusions P1-P5extending through sleeve bushing105. The apertures A1-A5respectively extend through the protrusions P1-P5of the annular portion102, such that the apertures A1-A5are defined by the softer material forming the protrusions P1-P5and the rest of annular portion102. Specifically, the apertures A1-A5extend from an inner end of the protrusions P1-P5to an outer surface of the annular portion102. In other embodiments, the protrusions P1-P5are omitted and the apertures A1-A5are at least partially defined by the sleeve bushing105. In other embodiments, the protrusions P1-P5are omitted and the bushing105can be located in front of the apertures A1-A5(i.e., with the chuck34located at the front of the hammer drill10), such that no portion of the bushing105intersects or overlaps the apertures A1-A5, as shown inFIG.26. In some embodiments, the bushing105may extend forward along the inner surface103toward a distal end107of the annular portion102, as shown inFIG.26.

In the illustrated embodiment shown inFIGS.4and6, only the ball98in aperture A5is shown, but each of the other apertures A1, A2, A3, and A4also contains a ball98. As shown inFIGS.2,5and7-25, the selector ring94includes a plurality of recesses R1, R2, R3, R4, and R5asymmetrically positioned about an inner periphery112of the selector ring94. The number of recesses R1-R5corresponds to the number of apertures A1-A5and the number of balls98within the respective apertures A1-A5.

In the illustrated embodiment, five apertures A1-A5, each containing a ball98, are located in the transmission housing30and five recesses R1-R5are defined in the selector ring94. However, in other embodiments, the hammer lockout mechanism90could employ more or fewer apertures, balls, and recesses. As shown inFIGS.5and7, the five apertures A1-A5are approximately located at 0 degrees, 55 degrees, 145 degrees, 221 degrees, and 305 degrees, respectively, measured in a counterclockwise direction from an oblique plane104containing a longitudinal axis108of the hammer drill10and bisecting aperture A1. As shown inFIGS.4and6, the first ratchet42and the first bearing50are set within a cylindrical cavity106defined within the annular portion102of the transmission housing30, and the selector ring94is radially arranged between the annular portion102and the collar74, surrounding the apertures A1-A5.

In operation, as shown inFIGS.4and5when the collar74and ring94are rotated together to a position corresponding to a “hammer drill” mode, all five apertures A1-A5are aligned with all five recesses R1-R5in the selector ring94, respectively. Therefore, when the spindle18is slid rearward relative to the transmission housing30in response to contact with a workpiece, the chamfered edge54of the first bearing50displaces the balls98situated in the respective apertures A1-A5radially outward and partially into the recesses R1-R5, thereby disabling the hammer lockout mechanism90. Thus, the first ratchet42is permitted to engage with the second ratchet46to impart reciprocation to the spindle18as it rotates.

As the spindle18reciprocates during “hammer drill” mode, the first bearing50reciprocates within the cavity106, causing the outer race52of the first bearing50to move along the inner surface103of the annular portion102. Because the outer race52slides along the sleeve bushing105, which is formed of a harder material than the rest of the annular portion102, the longevity of the transmission housing30, and the inner surface103of the annular portion102in particular, is increased compared to a transmission housing30without the sleeve bushing105. Through testing, it has been found that in absence of the bushing105, the spindle18experiences wobble at 6,000 reciprocation cycles of the bearing50. But, when the bushing105is used, the spindle18does not experience wobble even after 14,000 reciprocation cycles of the bearing50. The sleeve bushing105wears at a much lower rate than the inner surface103of the annular portion102, thus maintaining alignment of the spindle18with the longitudinal axis108of the hammer drill10throughout a longer period of the useful life of the hammer drill10.

When the collar74and selector ring94are incrementally rotated (e.g., by 18 degrees) in a counterclockwise direction to the second rotational position shown inFIGS.6and7, none of the apertures A1-A5are aligned with the recesses R1-R5. Thus, in this position of the collar74and selector ring94, the balls98in the respective apertures A1-A5are prevented from being radially displaced into the recesses R1-R5in response to the spindle18contacting a workpiece (via the chuck34and an attached drill or tool bit). Rather, the chamfered edge54of the first bearing50presses against the balls98, which in turn abut against the inner periphery112of the selector ring94and are inhibited from displacing radially outward. Thus, the spindle18is prevented from moving rearward, maintaining a gap110between the first and second ratchets42,46. Thus, in the second rotational position of the collar74and the selector ring94, the hammer lockout mechanism90is enabled, preventing the spindle18from reciprocating in an axial manner as it is rotated by the drive mechanism14, operating the hammer drill10in a “drill only” mode.

There are a total of twenty different positions between which the collar74and selector ring94can rotate, such that the collar74is rotated 18 degrees between each of the positions. The wiper is in electrical and sliding contact with the PCB82as the collar74is rotated between each of the twenty positions. Depending upon which of the electrical pads86on the PCB82the wiper contacts, the electronic clutch78adjusts which clutch setting to apply to the motor22. In the “hammer drill” mode and the “drill only” mode coinciding with the first and second rotational positions of the collar74and selector ring94, respectively, the electronic clutch78operates the motor22to output torque at a predetermined maximum value to the spindle18. In some embodiments, the predetermined maximum value of torque output by the motor22may coincide with the maximum rated torque of the motor22.

As shown inFIG.5and the Table below, the “hammer drill” position of the collar74corresponds to a “0 degree” or “first rotational position” position of the collar74, in which the recesses R1, R2, R3, R4, R5of the selector ring94are respectively and approximately located at 0, 55, 145, 221, and 305 degrees counterclockwise from the plane104, such that the apertures A1, A2, A3, A4, A5are thereby aligned. When the collar74is rotated 18 degrees counterclockwise from the “hammer drill” position to the “drill only” or “second rotational position” as shown inFIG.7, the recesses R1, R2, R3, R4, R5are respectively and approximately located at 18 degrees, 73 degrees, 163 degrees, 239 degrees, and 323 degrees counterclockwise from the plane104.

As shown in the Table below and inFIGS.8-25, the operator may continue to cycle through eighteen additional rotational positions of the collar74, each corresponding to a different clutch setting in “screwdriver mode”, by incrementally rotating the collar74counterclockwise by 18 degrees each time. The first clutch setting (FIG.8) provides a torque limit that is slightly less than the predetermined maximum value of torque output by the motor22available in the “hammer drill” mode or the “drill only” mode. As the clutch setting number numerically increases, the torque threshold applied to the motor22decreases, with the eighteenth clutch setting (shown inFIG.25) providing the lowest torque limit to the motor22.

As can be seen inFIGS.5and7-25, and the Table below, the “hammer drill” position inFIG.5is the only position in which all five apertures A1-A5are aligned with all five recesses R1-R5, thereby disabling the hammer lockout mechanism90as described above. In every other setting of the collar74and selector ring94, no more than two of any of the apertures A1-A5are aligned with the recesses R1-R5. Therefore, in “drill-only” mode (FIG.7) and “screwdriver mode” (FIGS.8-25, clutch settings1-18), at least three balls98inhibit the rearward movement of the spindle18, via the first bearing50, thereby enabling the hammer lockout mechanism90and preventing axial reciprocation of the spindle18as it rotates.

Degrees ofA1A2A3A4A5Balls inMode/Clutchcollar rotationAperture is aligned with which recess?recessesSettingFIG.0R1R2R3R4R55Hammer Drill518—————0Drill Only736—————01854R5R1———22972———R3R4231090——R2—R42411108—R5———1512126—————0613144R4—R1——2714162———R2R32815180—————0916198—R4R5——21017216R3——R1—21118234—————01219252————R211320270—R3—R5—21421288——R4R5—21522306R2———R121623324—————01724342—————01825360R1R2R3R4R55Hammer Drill5

To adjust the hammer drill10between “screwdriver” mode, “drill only” mode, and “hammer drill” mode, the collar74may be rotated a full 360 degrees and beyond in a single rotational direction, clockwise or counterclockwise, without any stops which would otherwise limit the extent to which the collar74may be rotated. Therefore, if the operator is using the hammer drill10in “screwdriver mode” on the eighteenth clutch setting (FIG.25), the operator needs only to rotate the collar74counterclockwise by an additional 18 degrees to switch the hammer drill10into “hammer drill” mode, rather than rotating the collar74in an opposite (clockwise) direction back through clutch settings 17 to 1 and “drill only” mode.

Various features of the invention are set forth in the following claims.