Drive assembly for an electric hand tool
OwnerTa-Chin Wanginventor
Life of this patent
Estimating the term…
Abstract
A drive assembly for an electric hand tool uses a ratchet and two opposed, spring-loaded pawls. The ratchet is integrally formed as a dovetail flange on the tool shaft inside a hollow rotor. The pawls are asymmetrical and pivotally mounted inside a recess in the rotor such that the centrifugal force generated by the rotation of the rotor causes the appropriate pawl to engage the ratchet and rotate the tool in the appropriate direction. When the rotor stops rotating, the spring causes the pawl to disengage from the ratchet and return to a rest position. This drive assembly is advantageous in that it completely does away with the noise generated by the gears in the conventional drive assembly and is much cheaper and more convenient to repair.
Claims9
A drive assembly for an electric hand tool comprising:
- a rotor (20) including a first end and a second end, a recess (21) defined between said two ends of said rotor (20) with at least one bridge (22) spanning said recess (21), said first end of said rotor (20) having a protrusion (201) extending therefrom, said protrusion (201) containing a keyed hole (202) in a center to receive a keyed shaft (11) of a reversible motor (10) and a second recess (203) on a forward end of said protrusion (201) aligned with said keyed hole (202), a through hole (205) define in said second end of said rotor (20) aligned with said second recess (203), said rotor (20) having a diameter parallel to said bridges (22), two second through hole (24) respectively defined near a end of said diameter of said rotor (20) orthogonal to a central diameter passing through said bridges (22);
- two second pins (241) each received in a corresponding pair of said second through holes (24) and having two ends respectively received in said first and second ends of said rotor (20);
- two stops (25) extending into said recess (21) and each having an axis parallel to the axis of said two second through holes (24);
- a tool shaft (40) rotatably mounted in said rotor (20), said tool shaft (40) having a first end extending through said through hole (205) and pivotally received in said second recess (203) on the front face of said rotor (20) protrusion (201), and a second endextending out through a front of said electric hand tool;
- at least one dovetail flange (41) extending radially out from a periphery of said tool shaft (40) in said recess (21) of said rotor (20), a total diameter at said dovetail flange (41) and said tool shaft (40) being smaller than a diameter of said through hole (205) of said rotor (20);
- a second bearing (205) mounted around said tool shaft (40) and securely received in said through hole (205) to prevent said tool shaft (40) from detaching from said rotor (20);
- a pawl device (30) having a first pawl (31) and a second pawl (32) each pivotally mounted in said recess (21) of said rotor (20) around said tool shaft (40) by said second pin (241) and aligning with each other to form a round passage (200) to selectively engaged with said dovetail flange (41) of said tool shaft (40), said round passage (200) having a diameter being slightly greater than said total diameter of said dovetail flange (41) and said tool shaft (40);
- a first spring (33) having a first end mounted on said bridge (22) and a second end mounted on said first pawl (31);
- and
- a second spring (34) having a first end mounted on said bridge (22) and a second end mounted on said second pawl (32).
Dependencies are inferred from the claim text.