Detection system for power equipment

• US 7,077,039 B2
• Filed: 11/12/2002
• Issued: 07/18/2006
• Est. Priority Date: 11/13/2001
• Status: Expired due to Term

• Current Assignee: Sawstop Holding LLC
• Original Assignee: SD3, LLC
• Inventors: Gass, Stephen F., Fulmer, J. David
• Primary Examiner(s): Eley, Timothy V.
• Assistant Examiner(s): PRONE, JASON D
• Application Number:
  US10/292,607
• Publication Number:
  US 20030090224A1
• Time in Patent Office: 1,344 Days
• Field of Search: 83D/IG.1, 83/58, 83/761, 833/70, 834/772, 83/62, 83/63, 83/72, 83 766- 769, 340/660, 340/686.6, 192/129.R, 192/125.R, 192/116.5, 342109-112, 318/362, 700/253, 700/255
• US Class Current: 83/13
• CPC Class Codes: B23D 59/005 for preventing collision of saw blades with other machine parts or workpieces
• CPC Class Codes: B23Q 11/0082 by determining whether the operator is in a dangerous position B23Q17/2438 takes precedence
• CPC Class Codes: B23Q 11/0092 actuating braking or stopping means
• CPC Class Codes: Y10S 83/01 Safety devices
• CPC Class Codes: Y10T 83/04 Processes
• CPC Class Codes: Y10T 83/088 Responsive to tool detector or work-feed-means detector
• CPC Class Codes: Y10T 83/091 Responsive to work sensing means
• CPC Class Codes: Y10T 83/162 With control means responsive to replaceable or selectable information program
• CPC Class Codes: Y10T 83/175 With condition sensor
• CPC Class Codes: Y10T 83/178 Responsive to work

Abstract

A machine is disclosed having a detection subsystem adapted to detect contact between a person and a specified portion of the machine, and to distinguish that contact from contact with other materials. The detection subsystem imparts an electrical signal to a specified portion of the machine, and distinguishes that contact based on a predetermined frequency response of the electrical signal. A reaction subsystem then causes a predetermined action to take place. The machine may be a power saw designed to minimize injury in the event a person accidentally contacts the blade.

Claims

1. A method of detecting contact between a human body material and a specified portion of a woodworking machine, and of distinguishing that contact from contact between at least one other material and the machine, the method comprising:

imparting an electrical signal on the specified portion of the machine, where the electrical signal includes at least two different frequency components;

measuring a characteristic of the electrical signal as a function of frequency when the specified portion is in contact with the human body material to obtain a first frequency response;

measuring the characteristic of the electrical signal as a function of frequency when the specified portion is in contact with the other material to obtain a second frequency response;

comparing the first and second frequency responses; and

setting frequency measurement parameters to distinguish human body material contact from contact by the other material.

2. The method of claim 1, where the machine is a power saw, where the specified portion is a blade, and where the method is employed to mitigate injury from contact between the human body material and the blade.

3. The method of claim 1, where the electrical signal imparted to the specified portion of the machine has a period comparable to the RC-time constant of a human body.

4. A method of detecting contact between a human body material and a specified portion of a woodworking machine, and of distinguishing that contact from contact between at least one other material and the machine, the method comprising:

imparting an electrical signal on the specified portion of the machine, where the electrical signal includes at least two different frequency components;

where the frequency components include a first frequency component having a period equal to or greater than the RC-time constant of a nominal human body and a second frequency component having a period less than the period of the first frequency component;

measuring a characteristic of the electrical signal as a function of frequency when the specified portion is in contact with the human body material to obtain a first frequency response;

measuring the characteristic of the electrical signal as a function of frequency when the specified portion is in contact with the other material to obtain a second frequency response;

comparing the first and second frequency responses; and

setting frequency measurement parameters to distinguish human body contact from contact by the other material.