Detection systems for power equipment
AssigneeSd3, LLC
InventorStephen F. Gass
Life of this patent
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Abstract
Methods to detect when a human body contacts a predetermined portion of a machine are disclosed. The methods distinguish contact with a person from contact with other materials. The methods are particularly applicable in woodworking equipment such as power saws to distinguish contact between a person and the blade of the saw from contact between the blade and wet or green wood. Woodworking machines and memory devices for use in woodworking machines having safety systems designed to detect a dangerous condition between a human and a dangerous portion of the woodworking machine and to trigger some action to mitigate the dangerous condition are also disclosed.
Claims5
A method of detecting a dangerous condition between a user and an operative element of a power tool:
- providing a detection system adapted to detect a dangerous condition between a user and the operative element of a power tool, where the detection is at least partially dependent on changes in the value of an electrical property sensed by the detection system;
- calibrating the detection system by establishing a nominal value for the electrical property when no dangerous condition is present;
- determining a current value of the electrical property when the operative element of the power tool is not operating;
- blocking operation of the operative element of the power tool if the current value is outside a predetermined range.
A method of reducing the chance of a false detection of a dangerous condition in a system designed to detect a dangerous condition between a user and a dangerous element of a machine comprising:
- providing a system configured to detect a dangerous condition between a user and a dangerous element of a machine, wherein the detection is based on the response of at least one detection scheme that has a response level that crosses a first threshold level when a dangerous condition is present, and wherein some events other than a dangerous condition can cause a response level in the detection scheme spanning the first threshold level for a dangerous condition, whereby such other events may cause the detection system to falsely detect a dangerous condition when no such dangerous condition is present;
- providing a response system configured to react to the detection of a dangerous condition, where the reaction involves emergency activation of a danger mitigation device outside the scope of the normal operation of the machine other than when a dangerous condition is detected;
- monitoring the response level while operating the machine;
- and
- stopping the machine without emergency activation of the danger mitigation device if the monitored response level crosses a second threshold that lies between a nominal response level of the detection system when no dangerous condition or other response level affecting events are present and the first threshold level.
Dependencies are inferred from the claim text.