The present invention relates to rotary tools and, more particularly, to a drive system for a rotary tool.
A rotary tool, such as an impact wrench, generally includes a housing supporting a motor, an output shaft having a first end adapted to engage a fastener and a second end having an anvil, and a drive mechanism operable to drive the output shaft. In impact wrenches, the drive mechanism generally includes one or more tilting hammers or dogs, which are rotated about a central axis by the motor and periodically impact the anvil to hammer or drive the output shaft in either a forward or a reverse direction. An operator generally toggles a switch located on the housing to change the rotation direction of the output shaft between the forward and reverse directions. Generally, the operator operates the tool in the forward direction to thread the fastener into engagement with a workpiece, and in a reverse direction to unthread the fastener from the workpiece.
When an operator tightens a fastener (e.g., a bolt, a screw, a nut, and the like) using a conventional impact wrench, the impact wrench may over-torque or over-tighten the fastener causing the fastener to break. Over-tightened fasteners may be difficult to loosen or remove from a workpiece.
Conventional impact wrenches often include a torque limiting mechanism that limits torque in both the forward and reverse directions. While it may be desirable to limit torque in the forward direction to prevent over-tightening, it is often desirable and/or necessary to have maximum torque in the reverse direction when, for example, the impact wrench is used to remove rusted, corroded, or damaged fasteners.
Conventional impact wrenches often include torque limiting mechanisms that limit the operating speed of the impact wrench. However, operators generally prefer impact wrenches that operate to quickly thread or unthread a fastener.
The present invention provides a rotary tool, such as an impact wrench, which, in one aspect of the invention, is operable in a forward mode and a reverse mode at a plurality of speeds. The plurality of speeds include a maximum speed. The rotary tool includes a housing having a forward end and a rearward end and defining an axis extending between the forward end and the rearward end. The rearward end supports a motor operable in a forward direction and a reverse direction. The rotary tool also includes an output shaft supported in the forward end of the housing and rotatable about the axis, and a hammer supported in the housing and operable to transfer a first rotational force from the motor to the output shaft in the reverse mode and a second rotational force from the motor to the output shaft in the forward mode. The first force is greater than the second force.
In another aspect of the invention, the rotary tool includes a housing having a forward end and supporting a motor. The motor has a motor shaft extending axially through the housing and defining an axis. The rotary tool also includes a frame supported in the housing and being rotatable relative to the housing about the axis, an output shaft supported in the forward end of the housing and rotatable about the axis, and a hammer pivotably coupled to the frame and defining a central aperture. The hammer has a first jaw and a second jaw extending into the central aperture. The first jaw and the second jaw are non-symmetrical.
In yet another aspect of the invention, the rotary tool includes a housing having a forward end and supporting a motor. The motor has a motor shaft extending axially through the housing and defining an axis. The rotary tool also includes a frame supported in the housing and being rotatable relative to the housing about the axis, and a hammer pivotably coupled to the frame and defining a central aperture. The hammer has a first jaw and a second jaw extending into the central aperture. The rotary tool also includes an output shaft supported in the forward end of the housing and being rotatable about the axis. The output shaft has an anvil extending axially through the central aperture. The first jaw lockingly engages the anvil in the reverse mode and the second jaw slidingly engages the anvil in the forward mode.
In still another aspect of the invention, the rotary tool includes a housing having a forward end and supporting a motor. The motor has a motor shaft extending axially through the housing and defining an axis. The rotary tool also includes a frame coupled to the motor shaft and rotatable relative to the housing about the axis in response to rotation of the motor shaft, and a hammer pivotably coupled to the frame and defining a central aperture. The hammer has a first jaw and a second jaw that extend into the central aperture. The first jaw defines a reverse engaging surface and the second jaw defines a forward engaging surface. The rearward engaging surface defines a reverse angle and the forward engaging surface defines a smaller forward angle. The rotary tool further includes an output shaft supported in the forward end of the housing and rotatable about the axis. The output shaft has an anvil extending axially through the central aperture. The forward engaging surface contacts the anvil at the forward angle and the reverse engaging surface contacts the anvil at the reverse angle.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.
The present invention is further described with reference to the accompanying drawings, which show various embodiments of the present invention. However, it should be noted that the invention as disclosed in the accompanying drawings is illustrated by way of example only. The various elements and combinations of elements described below and illustrated in the drawings can be arranged and organized differently to result in embodiments which are still within the spirit and scope of the present invention.
In the drawings, wherein like reference numerals indicate like parts:
a-6l are plan views of the portion of the rotary drive system shown in
a-7h are plan views of the portion of the rotary drive system shown in
As used herein and in the appended claims, the terms “upper”, “lower”, “first”, and “second” are for the purposes of description only and are not intended to imply any particular orientation, order, or importance.
A rotary tool, such as, for example, an impact wrench 10 embodying aspects of the present invention, is illustrated in FIG. 1. The impact wrench 10 includes a housing 12 having a forward end 16 and a rearward end 18, an operator's grip or handle 20, a motor 22 (e.g., an air motor or an electric motor) having a motor shaft 24, a trigger 26 operably coupled to the motor 22 to control motor speed, and a rotary drive system 28. The motor shaft 24 defines an axis 30, which extends axially through the impact wrench 10.
The rotary drive system 28 includes a frame or carrier 34 positioned in the forward end 16 of the housing 12. Bearing 35 supports the frame 34 in the housing 12 and facilitates rotation of the frame 34 about the axis 30 with respect to the housing 12. The frame 34 includes a forward plate 36 and a rearward plate 38, which together define a cavity or interior space 39. The forward and rearward plates 36, 38 are substantially similar and have generally ovular shapes. The plates 36, 38 are formed to include central apertures 40 opening along the axis 30 and through holes 42 positioned above and below the central apertures 40. Fasteners 44 (e.g., pins, rivets, screws, posts, bolts, and the like) extend through holes 42 in the forward and rearward plates 36, 38. As explained in greater detail below, during operation the fasteners 44 experience significant shearing stresses and are therefore preferably made of a relatively durable material (e.g., machine steel, stainless steel, and the like) and preferably have a relatively large cross sectional area. The central aperture 40 of the rearward plate 38 includes splines 45 which, matingly engage corresponding splines 46 on the motor shaft 24 to facilitate the transfer of rotational motion from the motor shaft 24 to the frame 34, as described in greater detail below.
The frame 34 also includes two hammers 48, 48′ positioned within the interior space 39 between the forward and rearward plates 36, 38. As shown in
The hammers 48, 48′ also define central apertures 62, which extend through the hammers 48, 48′ and open along the axis 30. Interior surfaces 64 of the hammers 48, 48′ define reverse jaws 66 and forward jaws 68 that both extend radially into the central apertures 62. As can be seen in
Together, the engaging surfaces 74 and the camming surfaces 76 define relatively sharply pointed outer edges 78. As shown in
The forward jaws 68 also include engaging surfaces 84 and camming surfaces 86 that intersect to define arcuately shaped outer edges 88. As shown in
The impact wrench 10 also includes an output shaft 92, which is rotatably supported in the forward end 16 by bushing 94 (see
With reference to
During operation, the impact wrench 10 is positioned in close proximity to a fastener (not shown) and the tool holder 98 is positioned to matingly engage the fastener. To tighten the fastener or thread the fastener into a workpiece (not shown), the impact wrench 10 is operated in a forward mode and to loosen the fastener or unthread the fastener from the workpiece, the impact wrench 10 is operated in a reverse mode.
Referring first to operation of the impact wrench 10 in the reverse mode, an operator moves a mode selector 112 (e.g., a toggle switch, a button, a dial, and the like) into a reverse position. The operator then depresses the trigger 26, causing power in the form of compressed air or electricity, to energize the motor 22. Because the user has selected the reverse mode, the motor shaft 24 rotates in a first or reverse direction (represented by arrow 114 in
The motor shaft 24 transfers rotational motion to the frame 34 via the mating engagement of splines 45, 46. The hammers 48, 48′ rotate with the frame 34 about the axis 30 and intermittently impact the anvils 102, 102′, hammering the anvils 102, 102′ in the reverse direction 114. This hammering motion is transferred via the anvils 102, 102′ and the output shaft 92 to the tool holder 98 (FIG. 1), which removes or unthreads the fastener from the workpiece.
a-6l detail the interaction of the hammers 48, 48′ and the anvils 102, 102′. For reasons of simplicity and brevity,
As shown in
As the hammer 48 rotates about the axis 30, the engaging surface 74 intermittently contacts the trailing edge 108 of the anvil 102. When the engaging surface 74 of the reverse jaw 66 contacts the trailing edge 108 of the anvil 102, the hammer 48 hammers the output shaft 92 in the reverse direction 114, which, in turn, rotates the fastener in a reverse direction. As shown in
Referring now to operation of the impact wrench 10 in the forward mode, the operator moves the mode selector 112 into a forward position. The operator then depresses the trigger 26, causing power in the form of compressed air or electricity to energize the motor 22. Because the user has selected the forward mode, the motor shaft 24 rotates in a second or forward direction (represented by arrow 116 in
The motor shaft 24 transfers rotational motion to the frame 34 via the mating engagement of splines 45, 46, as described above with respect to operation in the reverse mode. The hammer 48 rotates with the frame 34 about the axis 30. As the hammer 48 rotates, it intermittently impacts the anvil 102, applying a forward force (represented by arrow 117) to the anvil 102 and hammering the anvil 102 in the forward direction 116. This hammering motion is transferred via the anvil 102 and the output shaft 92 to the tool holder 98, which forces or hammers the fastener into the workpiece.
As shown in
In the second embodiment of the present invention, a hammer 248 is pivotably coupled to the frame 34 and defines a central aperture 262, which extends through the hammer 248 and opens along the axis 30. An interior surface 264 of the hammer 248 defines a reverse jaw 266 and a forward jaw 268 that both extend radially into the central aperture 262.
The reverse jaw 266 extends into the central aperture 262 and includes an engaging surface 274 and a camming surface 276. Together, the engaging surface 274 and the camming surface 276 define a relatively sharply pointed outer edge 278. As shown in
The forward jaw 268 extends into the central aperture 262. The forward jaw 268 also includes an engaging surface 284 and a camming surface 286, which intersect to define an arcuately shaped outer edge 288. As shown in
In the second embodiment, the output shaft 92 (see
Referring to
As shown in
During operation in the forward mode, the frame 34 rotates about the axis 30 in the forward direction 116 and the engaging surface 284 of the hammer 248 contacts the leading face 296 of the anvil 294, applying a forward force (represented by arrow 300) to the leading face 296. In the illustrated embodiment, the torque associated with the forward force 300 is preferably between about 40 ft-lbs and about 100 ft-lbs. However, because the outer edge 288 of the forward jaw 268 has a relatively large radius, the forward force 300 is significantly less than the reverse force 299.
After applying the forward force 300, the engaging surface 284 skips across the outer edge 298 of the forward jaw 268, causing the hammer 248 to pivot slightly about the fastener 44. This skipping action prevents the hammer 248 from fully impacting the leading edge 296 of the anvil 294. The camming surface 286 and the reverse jaw 266 then pass across the anvil 294. Additionally, because the impact with the leading edge 296 does not force the hammer 248 to rotate in a direction opposite the reverse direction 116, the hammer 248 is able to achieve higher rotational speeds in the forward mode than in the reverse mode. After passing the reverse jaw 266, the frame 34 and the hammer 248 rotate about the axis 30 until the engaging surface 284 of the forward jaw 268 contacts the leading face 296 of the anvil 294 again, initiating a second hammering impact.
The embodiments described above and illustrated in the drawings are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art, that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims.
For example, one having ordinary skill in the art will appreciate that the size and relative dimensions of the individual parts of the impact wrench can be changed significantly without departing from the spirit and scope of the present invention.
As such, the functions of the various elements and assemblies of the present invention can be changed to a significant degree without departing from the spirit and scope of the present invention.
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