Reciprocating Tool Biasing Assembly for Cam Float Prevention

Solution Overview

Problem

Reciprocating tools often experience reduced efficiency due to 'cam floating' at high speeds, where internal oscillations in springs cause the cam follower to lose contact with the cam, leading to incomplete orbital movement and increased power requirements, which reduces cutting efficiency and battery life.

Innovation Solution

An anti-cam float biasing assembly with a high spring constant outer biasing member and a low spring constant inner biasing member, where the inner member dampens the outer member to prevent oscillations and maintain contact between the cam follower and cam throughout the rotation, combined with a lever arm or slide control mechanism to ensure consistent orbital movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a spring with a higher spring constant is used to prevent cam floating, then contact between cam and cam follower is maintained, but frictional forces increase causing wear and power loss

Engineering Contradiction:

Improvecontact maintenanceVSAvoidfrictional power loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The spring system is segmented into two separate springs: a first spring providing the primary biasing force to maintain cam-follower contact, and a second spring providing damping force to reduce oscillations. This segmentation allows each spring to be optimized for its specific function, enabling reliable contact maintenance with lower overall spring constant and reduced frictional losses.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second spring acts as an intermediary damping element between the cam mechanism and the first spring. It absorbs and dissipates oscillatory energy through controlled deformation, reducing the transmission of harmful vibrations to the cam-follower interface while maintaining the necessary contact force.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a single high spring constant spring is used to prevent cam floating, then orbital movement is maintained at high speeds, but wear of cam and cam follower increases

Engineering Contradiction:

Improveorbital movement consistencyVSAvoidwear

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The spring system is segmented into two separate springs: a first spring providing the primary biasing force to maintain cam-follower contact, and a second spring providing damping force to reduce oscillations. This segmentation allows each spring to be optimized for its specific function, enabling reliable contact maintenance with lower overall spring constant and reduced frictional losses.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second spring converts the harmful oscillations and vibrations into beneficial controlled damping motion. By allowing the second spring to deform and dissipate energy, the system transforms harmful high-frequency vibrations into controlled, energy-absorbing deformation of the damping spring, protecting the cam-follower interface from wear.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If increased power is supplied to overcome friction from high spring constant, then cam floating is prevented, but power available for cutting operations decreases

Engineering Contradiction:

Improvecontact maintenanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The spring system is segmented into two separate springs: a first spring providing the primary biasing force to maintain cam-follower contact, and a second spring providing damping force to reduce oscillations. This segmentation allows each spring to be optimized for its specific function, enabling reliable contact maintenance with lower overall spring constant and reduced frictional losses.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the parameters of the spring system from a single high-stiffness spring to two springs with different stiffness characteristics. The first spring has a lower spring constant optimized for contact maintenance, while the second spring provides damping with its own optimized spring constant. This parameter change reduces the overall power consumption while maintaining reliability.

Inventive Principle:

Principle #35Parameter changes

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

The solution ensures complete orbital movement throughout the reciprocating cycle without significantly increasing power requirements, enhancing cutting efficiency and reducing wear and frictional losses, thus maintaining tool performance at high speeds.

Implementation Method 1

an outer biasing member (194) in the form of a spring and an inner biasing member (196) also in the form of a spring

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

the inner biasing member dampens the outer biasing member to prevent oscillations

Methodology Applied

Scientific EffectDamping: Damping

Data Source

PatentEP2969341B1Reciprocating tool with biasing assembly

Publication Date: 2019.01.30 ROBERT BOSCH GMBH

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AI summary

In one embodiment, a reciprocating tool includes a reciprocating plunger, a motor operably connected to the plunger, a cam portion operably connected to the motor, a cam follower operably connected to the reciprocating plunger, and a biasing assembly configured to bias the cam follower toward the cam portion, the biasing assembly including an outer biasing member and an inner biasing member, the inner biasing member in contact with an inner portion of the outer biasing member.