RECIPROCATING POWER TOOL

• US 20120192438A1
• Filed: 06/07/2011
• Published: 08/02/2012
• Est. Priority Date: 01/31/2011
• Status: Active Grant

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: HIRABAYASHI, Shinji, AOKI, Yonosuke
• Granted Patent: US 9,724,771 B2
• Time in Patent Office: Days
• US Class Current: 30/392
• CPC Class Codes: B23D 49/165 with means to move the saw blades in an orbital path
• CPC Class Codes: B23D 51/16 of drives or feed mechanisms for straight tools, e.g. saw blades, or bows

Abstract

It is an object of the invention to provide a technique for reducing vibration by counter weights which smoothly operate without linearly reciprocating, in a reciprocating power tool.

The reciprocating power tool has first and second bevel gears 123, 147 which are opposed to each other on either side of a pinion 119 and rotationally driven in opposite directions at the same reduction ratio by the pinion 119. Further, the reciprocating power tool has a slider 107 which is caused to linearly reciprocate in a longitudinal direction of a tool bit 111 by a crank 129. The first and second bevel gears 123, 147 are provided with first and second counter weights 143, 145 in positions displaced from their rotation axes, respectively. When the first counter weight 143 and the second counter weight 145 revolve, components of the revolving motion in the longitudinal direction of the tool bit oppositely move with respect to linear motion of the slider 107, and the first counter weight 143 and the second counter weight 145 move in the same phase in the longitudinal direction of the tool bit 111 and are disposed on opposite sides of the rotation axis and at the same distance from the rotation axis in a direction transverse to the longitudinal direction of the tool bit 111.

Claims

1. A reciprocating power tool, which performs a predetermined operation on a workpiece by reciprocating a tool bit in a longitudinal direction of the tool bit, comprising:

an output shaft that is driven by a motor,

a pinion that is provided on the output shaft,

a first bevel gear that is engaged with the pinion and rotationally driven around an axis extending transversely to the longitudinal direction of the tool bit,

a crank to which the first bevel gear is fixedly mounted and which converts rotation of the first bevel gear into linear motion,

a slider that holds the tool bit and is caused to linearly reciprocate in the longitudinal direction of the tool bit via linear motion of the crank,

a second bevel gear that is opposed to the first bevel gear on the same axis as a rotation axis of the first bevel gear and engaged with the pinion so as to be rotationally driven in a direction opposite to the first bevel gear,

a first counter weight that is disposed in a position displaced a predetermined distance from the rotation axis of the first bevel gear and rotates together with the first bevel gear, and

a second counter weight that is disposed in a position displaced a predetermined distance from the rotation axis of the second bevel gear and rotates together with the second bevel gear, wherein;

when the first counter weight and the second counter weight revolve around the rotation axis of the first bevel gear, components of the revolving motion in the longitudinal direction of the tool bit move opposite to linear motion of the slider, and the first counter weight and the second counter weight move in the same phase in the longitudinal direction of the tool bit with respect to each other and are disposed on opposite sides of said rotation axis at substantially the same distance from the rotation axis in a direction transverse to the longitudinal direction of the tool bit.

2. The reciprocating power tool as defined in claim 1, wherein the motor is disposed such that its rotation axis extends substantially in parallel to the longitudinal direction of the tool bit.

3. The reciprocating power tool as defined in claim 1, wherein the first bevel gear and the second bevel gear have the same number of teeth.

4. The reciprocating power tool as defined in claim 1, wherein the first bevel gear and the second bevel gear are formed by different methods.

5. The reciprocating power tool as defined in claim 1, wherein the second bevel gear is disposed between the first bevel gear and the slider in a direction of the rotation axis of the second bevel gear.

6. The reciprocating power tool as defined in claim 2, wherein the second bevel gear is disposed between the output shaft and the slider in a direction of the rotation axis of the second bevel gear.

7. The reciprocating power tool as defined in claim 1, comprising a power transmitting part for transmitting linear motion of the crank to the slider, wherein the slider which is driven to reciprocate in the longitudinal direction of the tool bit is supported both on opposite sides of the power transmitting part in a driving direction.

8. The reciprocating power tool as defined in claim 1, wherein the crank has a rotating shaft which rotates together with the first bevel gear, an eccentric pin which is disposed in a position displaced a predetermined distance from the rotation axis of the rotating shaft, and a crank plate which is provided on one end of the rotating shaft in its longitudinal direction and connects the rotating shaft and the eccentric pin to each other, and wherein the first counter weight is mounted on the crank plate, the second bevel gear is disposed on the crank plate side of the rotating shaft, and the second counter weight is disposed on a surface of the second bevel gear which faces the first counter weight.

9. The reciprocating power tool as defined in claim 8, wherein the first counter weight is fitted onto the eccentric pin and fastened to the crank plate at a position apart from the fitted part.

10. The reciprocating power tool as defined in claim 1, wherein the crank has a rotating shaft which rotates together with the first bevel gear, an eccentric pin which is disposed in a position displaced a predetermined distance from the rotation axis of the rotating shaft, and a crank plate which is provided on one end of the rotating shaft in its longitudinal direction and connects the rotating shaft and the eccentric pin to each other, and wherein the first bevel gear is fixedly mounted onto the rotating shaft and the rotating shaft is rotatably supported on opposite sides of the first bevel gear by bearings.

11. The reciprocating power tool as defined in claim 1, comprising a swinging driving part by which the slider holding the tool bit is caused to swing in a direction transverse to the longitudinal direction, in addition to being caused to reciprocate in the longitudinal direction by the crank.