Detection systems for power equipment
AssigneeSd3, LLC
InventorStephen F. Gass
Life of this patent
Estimating the term…
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 detect contact between a person and the blade of the saw. 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.
Claims11
A method for detecting contact between a user and a cutting tool on a piece of woodworking equipment, the method comprising:
- inducing an electrical signal on the cutting tool by generating an electrical current between a drive circuit and the cutting tool, wherein the electrical signal induced on the cutting tool has a phase and an amplitude, wherein the cutting tool has an apparent electrical impedance dependant at least in part on whether the cutting tool is in contact with the user, and wherein the electrical current, phase and amplitude are dependant at least in part on the apparent electrical impedance of the cutting tool;
- sampling one or more of the current, phase or amplitude a plurality of times at discrete intervals to generate multiple data points;
- calculating a value based at least in part on more than one of the data points;
- and
- deciding there has been contact between the user and the cutting tool if the value compares to a threshold in a predetermined way.
A method for detecting contact between a user and a cutting tool on a piece of woodworking equipment, the method comprising:
- applying an electrical signal to the cutting tool, wherein the cutting tool has an apparent electrical impedance dependant at least in part on whether the cutting tool is in contact with the user, and wherein the electrical signal applied to the cutting tool has an associated measurable characteristic that changes based on the apparent electrical impedance of the cutting tool;
- taking multiple measurements of the characteristic over time, wherein each measurement results in a data point;
- comparing one or more data points with one or more data points taken at one or more prior times;
- and
- deciding there has been contact between the user and the cutting tool if the data points compare in a predetermined way.
A method for detecting contact between a user and a cutting tool on a piece of woodworking equipment, the method comprising:
- applying an electrical signal to the cutting tool, wherein the cutting tool has an apparent electrical impedance dependant at least in part on whether the cutting tool is in contact with the user, and wherein the electrical signal applied to the cutting tool has one or more associated characteristics that change based on the apparent electrical impedance of the cutting tool;
- and
- a step for performing the function of deciding whether there has been contact between the user and the cutting tool based at least in part on accumulated changes over time of one or more of the associated characteristics.
Dependencies are inferred from the claim text.