Object proximity detection in a saw

Patent metadata

Field	Value
Publication number	US-10099399-B2
Application number	US-201615060670-A
Country	US
Kind code	B2
Filing date	Mar 4, 2016
Priority date	Mar 12, 2015
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

A method for detection of proximity between an object and an implement in a table saw includes operating a motor in the table saw to move the implement, generating, with a capacitive sensor formed in a throat plate around the implement in the table saw, a capacitance signal during operation of the motor, identifying, with a controller operatively connected to the capacitive sensor, an object in proximity to the capacitive sensor in response to a change in a level of capacitance in the capacitance signal, and deactivating, with the controller, the motor in the table saw in response to the change in the capacitance signal indicating a capacitance level that exceeds a predetermined threshold corresponding to a body part of an operator.

First claim

What is claimed:

1. A table saw comprising:
an implement extending through an opening in a throat plate;
a motor operatively connected to the implement;
a capacitive sensor positioned in the throat plate, the capacitive sensor comprising a plurality of capacitive sensing elements arranged in a predetermined two-dimensional arrangement on a surface of the capacitive sensor, the capacitive sensor being configured to generate a plurality of capacitance signals using the plurality of capacitive sensing elements during operation of the motor; and
a controller including a digital logic device operatively connected to the motor and the capacitive sensor, the controller being configured to:
operate the motor to move the implement;
identify an object in proximity to the capacitive sensor in response to a change in a level of capacitance in a plurality of capacitive signals generated by the plurality of capacitive sensing elements;
identify that the object corresponds to a body part of an operator in response to the change in the plurality of capacitance signals indicating a capacitance level that exceeds a predetermined threshold;

identify a location and a path of movement for the body part of the operator over the capacitive sensor based on the plurality of capacitance signals from the plurality of capacitive sensing elements in the capacitive sensor:
deactivate the motor in response to a trajectory of the path of movement of the body part intersecting the implement prior to contact between the body part of the operator and the implement while the location of the body part is outside of a predetermined distance of the implement; and
deactivate the motor in response to the location of the body part being within the predetermined distance of the implement.

2. The table saw of claim 1 , the controller being further configured to:
identify that the object corresponds to a work piece in response to the change in capacitance level being less than the predetermined threshold; and
continue operation of the motor to enable the implement to engage the workpiece.

3. The table saw of claim 1 , the controller being further configured to:
generate a warning signal for the operator in response to the location of the body part of the operator being outside of the predetermined distance of the implement.

4. The table saw of claim 1 further comprising:
an implement reaction mechanism; and
the controller being operatively connected to the implement reaction mechanism and further configured to:
activate the implement reaction mechanism in the saw in response to the trajectory of the path of movement of the body part intersecting the implement prior to contact between the body part of the operator and the implement while the location of the body part is outside of the predetermined distance of the implement; and
activate the implement reaction mechanism in the saw in response to the location of the body part being within the predetermined distance of the implement.

5. The table saw of claim 1 wherein the throat plate is formed from an electrical insulator to isolate the capacitive sensor from the implement.

Assignees

• Bosch Tool Corp
• Bosch Gmbh Robert

Inventors

• Laliberte Eric
• Volpert Dieter

Classifications

• B23D59/001 Primary

  Measuring or control devices, e.g. for automatic control of work feed pressure on band saw blade (measuring in general G01; controlling in general G05) · CPC title

• B23D47/025

  of tables · CPC title

• B23D47/08

  of devices for bringing the circular saw blade to the workpiece or removing same therefrom · CPC title

• G08B13/26

  by proximity of an intruder causing variation in capacitance or inductance of a circuit · CPC title

• B27G19/02 Primary

  for circular saws · CPC title