RECIPROCATING SAW

A reciprocating saw includes a housing, a motor positioned within the housing, the motor including a pinion rotatable about a motor axis, and a drive mechanism positioned within the housing and coupled to the motor. The drive mechanism includes a driven gear that engages the pinion and is rotated by the motor, and an output shaft driven by the motor to reciprocate relative to the housing. The output shaft is configured to support a tool element adjacent a forward portion of the housing. The drive mechanism includes a first counterweight coupled to the driven gear for rotation with the driven gear about a rotational axis, and a second counterweight spaced apart from the first counterweight and integrally formed with the driven gear. The first counterweight and the second counterweight are driven by the motor to rotate relative to the housing along a path.

FIELD OF THE INVENTION

The present invention relates to power tools, and more particularly to reciprocating saws.

BACKGROUND OF THE INVENTION

Power tools include different types of drive mechanisms to perform work. Power tools with reciprocating-type drive mechanisms commonly include counterweights to counterbalance forces generated by output elements (e.g., saw blades) during reciprocating movement.

SUMMARY OF THE INVENTION

The invention provides, in one aspect, a reciprocating saw including a housing, a motor positioned within the housing, the motor including a pinion rotatable about a motor axis, and a drive mechanism positioned within the housing and coupled to the motor, the drive mechanism including a driven gear that engages the pinion and is rotated by the motor, an output shaft driven by the motor to reciprocate relative to the housing, the output shaft configured to support a tool element adjacent a forward portion of the housing, a first counterweight coupled to the driven gear for rotation with the driven gear about a rotational axis, and a second counterweight spaced apart from the first counterweight and integrally formed with the driven gear, wherein the first counterweight and the second counterweight are driven by the motor to rotate relative to the housing along a path.

The invention provides, in another aspect, a reciprocating saw including a housing, a motor positioned within the housing, the motor including a pinion rotatable about a motor axis, and a drive mechanism positioned within the housing and coupled to the motor, the drive mechanism including a driven gear that engages the pinion and is rotated by the motor, an output shaft driven by the motor to reciprocate relative to the housing, the output shaft configured to support a tool element adjacent a forward portion of the housing, a first counterweight coupled to the driven gear for rotation with the driven gear about a rotational axis, a connecting rod pivotably coupled to the first counterweight at a first end thereof about a pivot axis, and a second counterweight spaced apart from the first counterweight and integrally formed with the driven gear, wherein the first counterweight and the second counterweight are driven by the motor to rotate relative to the housing along a path, wherein a center of mass of the first counterweight is offset from a reference plane intersecting and containing therein the rotational axis and the pivot axis.

The invention provides, in another aspect, a reciprocating saw including a housing, a motor positioned within the housing, the motor including a pinion rotatable about a motor axis, and a drive mechanism positioned within the housing and coupled to the motor, the drive mechanism including a driven gear that engages the pinion and is rotated by the motor, an output shaft driven by the motor to reciprocate relative to the housing along a spindle axis that is coaxial with the motor axis, the output shaft configured to support a tool element adjacent a forward portion of the housing, a first counterweight extending along a main axis and coupled to the driven gear for rotation with the driven gear about a rotational axis, a connecting rod pivotably coupled to the first counterweight at a first end thereof about a pivot axis, and a second counterweight spaced apart from the first counterweight and integrally formed with the driven gear, wherein the first counterweight and the second counterweight are driven by the motor to rotate relative to the housing along a path, wherein a center of mass of the first counterweight is offset from a reference plane intersecting and containing therein the rotational axis and the pivot axis, wherein operation of the reciprocating saw generates vibration in a first direction extending along an X-axis that is collinear with the spindle axis, and in a second direction extending along a Y-axis that is orthogonal to the spindle axis, and wherein the drive mechanism is configured to cut through a two-inch schedule 40 pipe with an X-axis vibration of 9 m/s2or less, while maintaining a Y-axis vibration of at least 5 m/s2, within a time period of less than 23 seconds.

DETAILED DESCRIPTION

FIGS.1-3illustrate a reciprocating saw10including a housing14, a motor18positioned within the housing14, and a drive mechanism22coupled to the motor18and positioned within the housing14. As shown inFIG.1, the housing14is comprised of two clamshell halves24A,24B that are connected along a plane25(FIG.3). In the illustrated embodiment, the clamshell halves24A,24B are secured together with threaded fasteners (e.g., screws), but may alternatively be secured together using other suitable coupling means.FIG.2illustrates the reciprocating saw10with one of the clamshell halves24A removed to illustrate the internal components (e.g., the motor18, the drive mechanism22, etc.) of the saw10.

Referring toFIG.1, the housing14includes a rearward portion26, a forward portion30, and a battery support portion34. The housing14also defines a longitudinal axis38(FIG.2) that extends through the rearward and forward portions26,30. The rearward portion26includes a D-shaped handle42, and the forward portion30includes a grip46. The D-shaped handle42and the grip46are configured to be grasped by a user during operation of the reciprocating saw10. An actuator or trigger50is supported by the rearward portion26adjacent the D-shaped handle42. The trigger50is actuatable by a user to selectively power the motor18. In the illustrated embodiment, the trigger50is positioned above the longitudinal axis38, and the longitudinal axis14generally divides the housing14into an upper section and a lower section. A shoe extends from and is pivotally coupled the forward portion30of the housing14. The shoe (not shown) pivots about a pivot axis and facilitates aligning the reciprocating saw10on a work piece to be cut.

The battery support portion34is formed on the rearward portion26of the housing14below the D-shaped handle42. In the illustrated embodiment, the battery support portion34is located beneath the longitudinal axis38of the housing14when the reciprocating saw10is viewed as shown inFIG.2. In other embodiments, the battery support portion34may be located elsewhere on the housing14. The battery support portion34is configured to receive a battery pack54(e.g., an 18-Volt Li-ion power tool battery pack) (FIG.1) and electrically connect the battery pack54to the motor18. In other embodiments, the battery pack54may have different voltages and/or chemistries. In still other embodiments, the reciprocating saw10may include a power cord such that the motor18is powered by an AC power source (e.g., a wall outlet, a portable generator, etc.).

As shown inFIG.2, the motor18is positioned within the housing14between the rearward portion26and the forward portion30. The motor18is also electrically connected to the battery pack54(or other suitable power source) through the trigger50and includes a motor shaft58and an output gear or pinion62. The motor shaft58defines a central axis, or motor axis70, of the motor18. In the illustrated embodiment, the motor axis70of the motor18is generally aligned or coaxial with the longitudinal axis38of the housing14. When powered, the motor18rotates the motor shaft58and the pinion62about the axis70to drive the drive mechanism22.

As shown inFIGS.2and3, the drive mechanism22is positioned at least partially within the forward portion30of the housing14between the motor18and the shoe. The illustrated drive mechanism22is a slider-crank mechanism that includes a driven gear74, a connecting rod78, and an output shaft82. The driven gear74engages the pinion62of the motor18and defines a central axis86about which the gear74rotates. In the illustrated embodiment, the central axis86is perpendicular to the longitudinal axis38of the housing14and extends between opposing sides of the housing14. More particularly, the central axis86is perpendicular to the plane25(FIG.3) along which the clamshell halves24A,24B of the housing14are connected. The driven gear74is thereby vertically oriented within the housing14. With reference toFIG.6, the saw10additionally includes one or more cylindrical sleeves88surrounding the shaft82. Specifically, sleeves88are positioned within a bushing assembly92which, in turn, is supported within the housing14.

The longitudinal axis38of the housing14and the motor axis70of the motor18extend through a center of the gear74(i.e., through the central axis86) to divide the gear74into a first, or upper, portion90and a second, or lower, portion94. In the illustrated embodiment, the upper portion90of the driven gear74is located on the same side of the longitudinal axis38as the output shaft82and the trigger50, while the lower portion94of the driven gear74is located on the same side of the longitudinal axis38as the battery support portion34. In other embodiments, the output shaft82may be located on the opposite side of the longitudinal axis38such that the lower portion94of the driven gear74is located on the same side of the longitudinal axis38as the output shaft38. It should be understood what constitutes the upper and lower portions90,94of the driven gear74changes during operation of the drive mechanism22because the gear74rotates. The terms “upper” and “lower” are simply illustrative terms used to help describe volumes of spaces above and below the axes38,70that are occupied by sections of the gear74at any given time. At any particular instance in time, the actual section of the gear74that qualifies as the “upper portion” or the “lower portion” is different than at another instance in time.

The connecting rod78, or drive arm, includes a first end that is coupled to the driven gear74by a crank pin98and a second end that is coupled to the output shaft82by a pivot pin102. The crank pin98is offset from the central axis86of the driven gear74such that, as the gear74is rotated, the crank pin98moves about the central axis86. As the first end of the connecting rod78moves with the driven gear74, the second end of the connecting rod78pushes and pulls the output shaft82in a reciprocating motion. The crank pin98allows the connecting rod78to pivot vertically relative to the driven gear74, while the pivot pin102allows the connecting rod78to pivot vertically relative to the output shaft82.

The output shaft82, or spindle, reciprocates within the forward portion30of the housing14generally along a spindle axis106. In the illustrated embodiment, the spindle axis106is generally parallel to and positioned above the longitudinal axis38of the housing14. Rotary motion of the motor18is thereby translated into linear reciprocating motion of the output shaft82by the driven gear74and the connecting rod78.

The motor axis70and the spindle axis106together define a plane. The driven gear74is vertically oriented within the housing14in that the gear74rotates about an axis (i.e., the central axis86) that is perpendicular to the plane defined by the motor and spindle axes70,106. In the illustrated embodiment, the plane defined by the motor and spindle axis70,106is the same as the plane25(FIG.3) along which the clamshell halves24A,24B are coupled together. In other embodiments, one or both of the motor and spindle axes70,106may be offset from, yet still parallel to the plane25.

With continued reference toFIG.2, a blade clamp110is coupled to an end of the output shaft82opposite from the connecting rod78. The blade clamp110receives and secures a saw blade, or other tool element, to the output shaft82for reciprocating movement with the output shaft82. The output shaft82supports the saw blade such that, during operation of the reciprocating saw10, the drive mechanism22moves the saw blade through a cutting stroke when the output shaft82is pulled by the connecting rod78from an extended position to a retracted position, and through a return stoke when the output shaft82is pushed by the connecting rod78from the retracted position to the extended position.

With reference toFIG.4, the illustrated drive mechanism22also includes a first counterweight114and a second counterweight116. The first and second counterweights114,116help balance forces generated by the output shaft82and pin102during reciprocating movement. In the illustrated embodiment, the first counterweight114and the second counterweight116are separate elements but may alternatively be integrally formed as a single piece. More specifically, the second counterweight116and the driven gear74are integrally formed as a single piece, and the first and second counterweights114,116are spaced apart from each other along the axis86. In alternative embodiments, the second counterweight116and the driven gear74may be separate components.

The illustrated first counterweight114includes a hub or connection portion118and a mass portion122. The connection portion118is pivotably coupled to the connecting rod78via the crank pin98. A first guide pin126also extends from the connection portion118and is rotatably supported within the housing14by a bushing128. The first guide pin126(FIGS.3-4) supports the first counterweight114within the housing14and defines an axis of rotation130of the first counterweight114. In the illustrated embodiment, the axis of rotation130of the first counterweight114and the central axis86of the driven gear74(i.e., the second counterweight116) are coaxial so that the first counterweight114and the driven gear74(and the second counterweight116) rotate about the same axis. Similar to the driven gear74, the first counterweight114is, therefore, also vertically oriented within the housing14. In the illustrated embodiment, the axis of rotation130intersects and is perpendicular to the motor axis70.

The mass portion122of the first counterweight114extends from the connection portion118and includes a majority of the mass of the first counterweight114. More specifically, the mass portion122of the first counterweight114extends in a radially outward direction from the connection portion118. In the illustrated embodiment, the mass portion122has a generally semi-circular shape to match the circular shape and contour of the driven gear74. That is, the first counterweight114is shaped and sized so it lies within a vertical footprint area defined by the driven gear74. Such an arrangement reduces the amount of space required within the housing14to accommodate the counterweight114. In other embodiments, the mass portion122may have other suitable shaped or configurations.

The second counterweight116additionally includes a connection portion120and a mass portion124. As shown inFIGS.3-4, the hub or connection portion120of the second counterweight116is integral with the driven gear74. The connection portion120is pivotably coupled to the connecting rod78via the crank pin98. A second guide pin132also extends from the connection portion120and is rotatably supported within the housing14by a bearing142. The second guide pin132supports the second counterweight116and the driven gear74within the housing14along the axis of rotation130of the first counterweight114and the central axis86of the driven gear74.

The mass portion124of the second counterweight116extends from the connection portion120in a radially outward direction. The mass portion124of the second counterweight116is offset from the mass portion122of the first counterweight114in a direction parallel with the rotational axis130of the first counterweight114. The mass portion124of the second counterweight116has a generally semi-circular shape and matches the circular shape and contour of the driven gear74. Specifically, the mass portion124of the second counterweight116lies within the vertical footprint area defined by the driven gear74, and aligns the first and second counterweights114,116. This arrangement reduces the amount of space required within the housing14to accommodate the second counterweight116. In other embodiments, the mass portion124of the second counterweight116may have other suitable shaped or configurations.

With continued reference toFIGS.2and4, the crank pin98aligns the first counterweight114and the driven gear74such that the first and second mass portions122,124are substantially aligned. Therefore, movement of the mass portions122,124in a direction opposite the movement of the output shaft82tends to balance the forces generated during reciprocation of the saw blade in a front-to-back direction.

As the driven gear74rotates and drives the crank pin98, the mass portions122,124are moved in a substantially opposite direction than the output shaft82to counterbalance the inertial forces of the output shaft82and attached saw blade. In particular, the mass portions122,124are in a first position (e.g., relatively close to the motor18and relatively far from the output shaft82), as shown inFIG.2, when the output shaft82is in the extended position. The mass portions122,124rotate to a second position (e.g., relatively close to the output shaft82and relatively far from the motor18) when the output shaft82is in the retracted position. Furthermore, as shown inFIG.5, the first counterweight114defines a reference plane134that intersects and contains therein the rotational axis130of the counterweight114and a pivot axis136(FIGS.2-3) of the crank pin98. The first counterweight114includes a phase angle A (FIG.5) extending between the reference plane134and a line of action138intersecting a center of mass140of the counterweight114and the rotational axis130of the first counterweight114. In the illustrated embodiment, the phase angle A is 21 degrees. The phase angle A is sized such that the center of mass140of the first counterweight114is very near its rearmost position along a circular path P (FIG.2) when the output shaft82is at its forwardmost (i.e., extended) position. Also, when the output shaft82is at its forwardmost position, the center of mass140of the first counterweight114is intersected by the longitudinal axis38.

In the illustrated embodiment, the counterweights114,116rotate along a path P in a clockwise direction (when viewing the reciprocating saw10as shown inFIG.2) about the axis of rotation130between the first and second positions. That is, the mass portions122,124of the counterweights114,116travel generally above the longitudinal axis38of the housing14during the cutting stroke of the output shaft82to move from the first position to the second position. The mass portion124of the second counterweight116is rotationally aligned and in phase with the mass portion122of the first counterweight114along the path P. Conversely, the mass portions122,124of the counterweights114,116travel generally below the longitudinal axis38of the housing14during the return stroke of the output shaft82to move from the second position to the first position. Stated another way, as the mass portions122,124of the counterweights114,116move through a rearward half of the path P (i.e., the half of the path P that is closer to the rearward portion26of the housing14) at the end of the return stroke and start of the cutting stroke, the mass portions122,124generally move in an upward direction (as viewed inFIG.2) and toward the spindle axis106. As the mass portions122,124of the counterweights114,116move through a forward half of the path P (i.e., the half of the path P that is closer to the forward portion30of the housing14) at the end of the cutting stroke and start of the return stroke, the mass portions122,124generally move in a downward direction (as viewed inFIG.2) and away from the spindle axis106. This movement of the first and second counterweights114,116causes the front of the saw10to tend to move into a work piece (downward inFIG.2) as the cutting stroke begins.

In the illustrated embodiment, the mass of various components of the drive mechanism (e.g., the output shaft82, the crank pin98, etc.) is reduced. As a result, the mass of the first counterweight114may be reduced and distributed into the second counterweight116, as discussed above, while also allowing for an increase in stroke length of the output shaft82. In the illustrated embodiment, the stroke of the output shaft82is 1.25 inches, an increase of 10% over prior art reciprocating saws of a similar size but with a single counterweight integrally formed with the drive gear.

Because the first counterweight114is coupled to the driven gear74by the crank pin98, the first counterweight114and the second counterweight116rotate together through the path P. As discussed above, the terms “upper portion” and “lower portion” of the driven gear74refer to volumes of space occupied by sections of the gear74during operation of the drive mechanism22.

The arrangement of the first counterweight114and the driven gear74increases cutting performance of the reciprocating saw10compared with rotation of the first and second counterweights114,116in the opposite direction (e.g., counterclockwise when viewing the reciprocating saw10as shown inFIG.2). In particular, the mass portions122,124of the counterweights114,116tend to move the saw10in the cutting direction during the non-cutting stroke, which helps drive the reciprocating saw10and the saw blade into the work piece at the start of the next cutting stroke. In contrast, if the counterweights114,116are rotated in the opposite direction, the reciprocating saw10and the saw blade may tend to move away from the work piece during the start of the next cutting stroke. By rotating the counterweights114,116in the clockwise direction R, a user can more easily initiate cuts into a work piece and significantly reduce the amount of time required to cut through the work piece. In the illustrated embodiment, the saw10is capable of cutting through a two-inch schedule 40 pipe in less than 23 seconds. In some embodiments, the saw10is capable of cutting through a two-inch schedule 40 pipe in 21.9 seconds. Additionally, by rotating the counterweights114,116in the clockwise direction R, the time for cutting through a piece of 2″×12″ wood or other lumber is reduced compared to rotating the counterweights114,116in an opposite (i.e., counter-clockwise) direction.

During operation of the saw10, vibration generated by the reciprocating saw10may fluctuate in a horizontal direction and a vertical direction. With reference toFIG.2, the horizontal direction is the direction extending along an X-axis144. The X-axis144extends along and is collinear with the spindle axis106. The vertical direction is the direction extending along a Y-axis148. The Y-axis148is substantially orthogonal to the spindle axis106of the rotational axes86,130of the driven gear74and the counterweights114,116. Furthermore, vibration may fluctuate in a direction extending along a Z-axis152(FIG.3). The Z-axis152is positioned substantially orthogonal to both the X-axis144and the Y-axis148and extends along and is collinear with the rotational axes86,130of the driven gear74and counterweights114,116. The velocity of the saw10lags its acceleration. Thus, the velocity of the counterweights114,116in the clockwise-rotating saw10is downward at the end of the return stroke and at the beginning of the cutting stroke. This downward velocity results in a force that drives the saw10, and more particularly the saw blade, into a work piece to start cutting the work piece. Due to the reduced mass of the drive mechanism22and the increased stroke length, the vibration generated in the vertical direction may be maximized, and the vibration in the horizontal direction, which is that most readily perceived by an operator of the saw10, may be minimized. During no-load testing (i.e., without an attached saw blade), in one embodiment as shown inFIG.7, it was determined that the magnitude of vibration of the saw10is approximately 6.5 m/s2in the vertical direction (i.e., along the Y-axis), whereas the magnitude of vibration of the saw10is less than 8 m/s2in the horizontal direction (i.e., along the X-axis), and in some embodiments approximately 7.5 m/s2or less. In other embodiments, the magnitude of vibration of the saw10is approximately 5.75 m/s2in the vertical direction (i.e., along the Y-axis), whereas the magnitude of vibration of the saw10is less than 9 m/s2in the horizontal direction (i.e., along the X-axis). As mentioned above, X-axis vibration is more readily perceived by an operator of the saw10, and Y-axis vibration has some attendant benefits (e.g., plunging the saw blade into the workpiece during a cutting stroke). Therefore, it is desirable to minimize X-axis vibration while not attenuating, or in some embodiments increasing, Y-axis vibration, both of which are accomplished with the saw10.