System and method for identification of implement motion in a power tool

Patent metadata

Field	Value
Publication number	US-9952583-B2
Application number	US-201313827897-A
Country	US
Kind code	B2
Filing date	Mar 14, 2013
Priority date	Sep 28, 2012
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A method of operating a power tool identifies motion of an implement in a power tool. The method includes obtaining a plurality of samples of an electrical signal that passes through the implement, identifying a parameter for the plurality of samples corresponding to a variation in values of predetermined groups of samples in the plurality of samples, updating a status for the implement with a first status indicating that the implement is not moving with reference to the identified parameter being less than a predetermined threshold, and updating a status for the implement with a second status indicating that the implement is moving with reference to the identified parameter being greater than the predetermined threshold.

First claim

What is claimed:

1. A method for identifying motion of an implement in a power tool comprising:
generating, with a clock source in the power tool, a time varying electrical signal that passes through the implement;
obtaining, with a controller in the power tool, a plurality of samples of the electrical signal that passes through the implement during a period in which an actuator that is operatively connected to the implement to move the implement is deactivated;
identifying, with the controller, a parameter for the plurality of samples corresponding to a variation in values of predetermined groups of samples in the plurality of samples, the identifying comprising:
identifying, with the controller, a variance for each group of samples in a plurality of at least two groups of samples of the electrical signal; and
generating, with the controller, a summed variance parameter as a sum of the variance for one group of samples with the variance for another group of samples in the at least two groups of samples;

updating, with the controller, a status for the implement stored in a memory within the power tool with a first status indicating that the implement is not moving with reference to the identified parameter being less than a predetermined threshold, the updating of the first status further comprising:
comparing, with the controller, the summed variance parameter to the predetermined threshold; and
updating, with the controller, the status for the implement with the first status indicating that the implement is not moving in response to both the summed variance parameter and another summed variance parameter identified in a previous plurality of groups of samples being less than the predetermined threshold;

updating, with the controller, a status for the implement in the memory with a second status indicating that the implement is moving with reference to the identified parameter being greater than the predetermined threshold; and
activating, with the controller, an arrest mechanism in the power tool to halt or retract the implement while the actuator is deactivated only in response to the status of the implement being the second status and in further response to detection of contact between a human operator and the implement.

2. The method of claim 1 , the updating of the status with the second status further comprising:
comparing, with the controller, the summed variance parameter to the predetermined threshold; and
updating, with the controller, the status for the implement with the second status indicating that the implement is moving in response to both the summed variance parameter and another summed variance parameter identified in a previous plurality of groups of samples being greater than the predetermined threshold.

3. A power tool comprising:
an actuator configured to move an implement;
a clock source configured to generate a time varying electrical signal that passes through the implement;
a memory;
an arrest mechanism configured to halt motion of the implement or retract the implement from contact with a human operator; and
a controller operatively connected to the actuator, the memory, and the arrest mechanism, the controller being configured to:
obtain a plurality of samples of the electrical signal during a period in which the actuator is deactivated;
identify a parameter for the plurality of samples corresponding to a variation in values of predetermined groups of samples in the plurality of samples, the controller being further configured to:
identify a variance for each group of samples in a plurality of at least two groups of samples of the electrical signal; and
generate a summed variance parameter as a sum of the variance for one group of samples with the variance for another group of samples in the at least two groups of samples;

update a status for the implement stored in the memory with a first status indicating that the implement is not moving with reference to the identified parameter being less than a predetermined threshold stored in the memory, the controller being further configured to:
compare the summed variance parameter to the predetermined threshold; and
update the status for the implement in the memory with the first status indicating that the implement is not moving in response to both the summed variance parameter and another summed variance parameter identified in a previous plurality of groups of samples being less than the predetermined threshold in the memory;

update the status for the implement in the memory with a second status indicating that the implement is moving with reference to the identified parameter being greater than the predetermined threshold stored in the memory; and
activate the arrest mechanism to halt or retract the implement while the actuator is deactivated only in response to the status of the implement being the second status and in further response to detection of contact between the human operator and the implement.

4. The power tool of claim 3 , the controller being further configured to:
compare the summed variance parameter to the predetermined threshold; and
update the status for the implement in the memory with the second status indicating that the implement is moving in response to both the summed variance parameter and another summed variance parameter identified in a previous plurality of groups of samples being greater than the predetermined threshold in the memory.

Assignees

• Bosch Tool Corp
• Bosch Gmbh Robert

Inventors

• Mangapuram Sai Yogesh Kumar
• Ramaswamy Bharadwaja Maharshi
• Krishnarao Niranjan Sathyanarayanarao
• Srikantiah Vishwanatha Manevarthe

Classifications

• G01P13/00 Primary

  Indicating or recording presence, absence, or direction, of movement (electric switches H01H; counting moving objects G06M7/00) · CPC title

• B23Q11/0082

  by determining whether the operator is in a dangerous position (B23Q17/2438 takes precedence) · CPC title

• G05B19/406 Primary

  characterised by monitoring or safety (G05B19/19 takes precedence) · CPC title