Apparatus and method for detecting dangerous conditions in power equipment

• US 7,640,835 B2
• Filed: 10/22/2007
• Issued: 01/05/2010
• Est. Priority Date: 08/14/2000
• Status: Expired due to Term

• Current Assignee: Sawstop Holding LLC
• Original Assignee: SD3, LLC
• Inventors: Gass, Stephen F.
• Primary Examiner(s): Alie; Ghassem
• Application Number:
  US11/975,985
• Publication Number:
  US 20080041204A1
• Time in Patent Office: 806 Days
• Field of Search: 83/621, 83D/IG.1, 83/58, 834/713, 834/771, 834/90, 835/89, 833/971, 834/772, 832/97, 836/44, 320/166, 320/562, 320/658, 320/663, 320665-668, 320/675, 320/686, 320/688, 320/698, 361/181, 361/281, 361/286, 361/179
• US Class Current: 83/13
• CPC Class Codes: B23D 59/001 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 Class Codes: B23Q 11/0082 by determining whether the operator is in a dangerous position B23Q17/2438 takes precedence
• CPC Class Codes: B27B 13/14 Braking devices specially designed for band sawing machines, e.g. acting after damage of the band saw blade
• CPC Class Codes: B27B 5/38 Devices for braking the circular saw blade or the saw spindle; Devices for damping vibrations of the circular saw blade, e.g. silencing B23D47/005 takes precedence
• CPC Class Codes: B27G 19/00 Safety guards or devices specially adapted for wood saws; Auxiliary devices facilitating proper operation of wood saws
• CPC Class Codes: B27G 19/02 for circular saws
• CPC Class Codes: F16P 3/12 with means, e.g. feelers, which in case of the presence of a body part of a person in or near the danger zone influence the control or operation of the machine F16P3/08 takes precedence
• CPC Class Codes: F16P 3/145 using magnetic technology
• CPC Class Codes: F16P 3/148 using capacitive technology
• CPC Class Codes: Y10S 83/01 Safety devices
• CPC Class Codes: Y10T 83/04 Processes
• CPC Class Codes: Y10T 83/081 With randomly actuated stopping means
• CPC Class Codes: Y10T 83/089 Responsive to tool characteristic
• CPC Class Codes: Y10T 83/707 By endless band or chain knife
• CPC Class Codes: Y10T 83/7693 Tool moved relative to work-support during cutting
• CPC Class Codes: Y10T 83/7726 By movement of the tool
• CPC Class Codes: Y10T 83/7788 Tool carrier oscillated or rotated

Abstract

Woodworking machines are disclosed having electrically conductive cutting tools adapted to cut workpieces. The machines include a contact detection system capacitively coupled to the cutting tool, and adapted to detect contact between a person and the cutting tool. The machines also include a reaction system configured to cause one or more predetermined actions to take place upon detection of contact between a person and the cutting tool by the contact detection system.

Claims

1. A method of detecting a dangerous condition between a person and a woodworking machine, where the woodworking machine includes a cutting tool electrically coupled to an arbor, and where the cutting tool and arbor are electrically isolated, the method comprising:

imparting an electrical signal to the cutting tool through a capacitive coupling that includes two spaced-apart conductors, where at least a portion of the surface of the arbor is one of the conductors; and

monitoring the electrical signal for changes indicative of the dangerous condition.

2. The method of claim 1 where the dangerous condition is contact between the person and the cutting tool.

3. The method of claim 1 where the dangerous condition is proximity between the person and the cutting tool.

4. The method of claim 1 where one of the two spaced-apart conductors is a charge plate positioned adjacent the surface of the arbor, and where the limitation of imparting an electrical signal to the cutting tool comprises inducing an electrical charge on the arbor by imparting an electrical charge to the charge plate.

5. The method of claim 1 where the limitation of monitoring the electrical signal for changes comprises using the electrical signal imparted to the cutting tool to induce an electrical charge on a sense electrode positioned adjacent the surface of the arbor, and analyzing the electrical charge on the sense electrode for predetermined characteristics.