Reciprocating Power Tool Vibration Reduction via Counterweight Inversion

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Solution Overview

Problem

Existing reciprocating power tools, such as saws, experience vibration issues due to the counterweight's linear reciprocating motion, which causes energy loss and unnecessary vibration when reversing direction.

Innovation Solution

The implementation of a counterweight mechanism involving two bevel gears rotating in opposite directions around the crank axis, with the first counterweight mounted on the driving bevel gear and the second counterweight on the counterrotating bevel gear, cancels out momentum in the longitudinal direction and transverse to it, reducing vibration without linear reciprocating motion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a counter weight reciprocates linearly in a direction opposite to the slider, then vibration caused by reciprocating motion of the slider is reduced, but vibration is caused by collision when the counter weight reverses its direction of movement and energy loss is caused by the reversal of direction

Engineering Contradiction:

ImprovevibrationVSAvoidenergy loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The invention inverts the conventional linear reciprocating motion of the counter weight into rotational motion. The counter weight is mounted on the bevel gear and rotates together with it, changing the motion trajectory from linear back-and-forth to circular rotation, thereby eliminating collision during direction reversal

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention makes the counter weight's motion dynamic by coupling it to the rotating bevel gear through which it rotates. This dynamic rotational motion allows the counter weight to smoothly change direction without collision, as rotation naturally transitions through all angles without abrupt reversals

Inventive Principle:

Principle #15Dynamics

2Object-affected harmful factors

If a counter weight reciprocates linearly in a direction opposite to the slider, then vibration caused by reciprocating motion of the slider is reduced, but the counter weight causes collision when reversing its direction of movement

Engineering Contradiction:

ImprovevibrationVSAvoidvibration from collision

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention applies curved rotational motion to the counter weight through the bevel gear mechanism. The counter weight follows a circular path during rotation, using curved motion to smoothly transition between positions without the abrupt linear direction changes that cause collision

Inventive Principle:

Principle #14Spheroidality (Curvature)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively reduces vibration by synchronizing the movement of counterweights with the slider's reciprocating motion, enhancing stability and cutting efficiency while preventing unnecessary vibration and energy loss.

Implementation Method 1

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

Methodology Applied

Scientific EffectGear mechanism: Gear

Implementation Method 2

components of the revolving motion in the longitudinal direction of the tool bit move opposite to linear motion of the slider

Methodology Applied

Scientific EffectMomentum cancellation: Conservation of Momentum

Implementation Method 3

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

Methodology Applied

Scientific EffectCrank mechanism: Crankshaft

Implementation Method 4

the momenta of the slider and the counter weight which mainly includes inertial force can cancel each other out

Methodology Applied

Scientific EffectInertial force: Inertia

Data Source

PatentUS9724771B2Reciprocating power tool

Publication Date: 2017.08.08 MAKITA CORP

AI summary

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.