Detection system for power equipment

• US 8,438,958 B2
• Filed: 12/19/2011
• Issued: 05/14/2013
• Est. Priority Date: 08/14/2000
• Status: Expired due to Term

• Current Assignee: Sawstop Holding LLC
• Original Assignee: SD3, LLC
• Inventors: Gass, Stephen F., Chamberlain, Robert L., Schramm, Benjamin B., Jensen, Joel F., Betts-LaCroix, Jonathan N.
• Primary Examiner(s): PRONE, JASON D
• Application Number:
  US13/374,290
• Publication Number:
  US 20120167732A1
• Time in Patent Office: 512 Days
• Field of Search: 83D/IG.1, 83/58, 83/62, 83/621, 83/63, 83/72, 83/767, 837/88, 835/81, 834/712, 834/771, 834/772, 835/221.2, 835/26, 833/971, 144/154.5, 144/356, 144/384, 144/391, 144/427, 144/286.5, 297/08, 292/54, 294/13, 324/550, 324/424, 408/5, 56/109, 56/113, 192/192.A, 192/129.R, 192/130, 102/202.7, 89/15.6, 137/68.12, 137/72, 137/76, 188/5, 188/6, 188/110, 188/189, 169/57, 169/59, 169/42, 169/DIG.3, 74/2, 403/2, 403/28, 411/2, 411/39, 411/390, 335/1, 335/242, 335/132, 318/362, 241/32.5, 337/239, 337/148, 337/1, 337/5, 337/10, 337/17, 337/140, 337/170, 337/190, 337/237, 337/401, 337/290, 337/404, 337/405, 218/2, 218/154, 307/639, 307/328, 307/115, 307/326, 307/142, 307/117, 307/126, 307/131, 451/409, 280/806, 297/480, 187/69, 187/77, 187/89, 187/189, 187/216, 187/166, 187/72.3, 340/679, 340/680, 340/686.1, 340/687, 340/686.3, 340/686.6
• US Class Current: 83/62
• CPC Class Codes: B23D 47/025 of tables
• CPC Class Codes: B23D 47/08 of devices for bringing the circular saw blade to the workpiece or removing same therefrom
• 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: B26D 7/24 arranged to disable the operating means for the cutting member
• 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: B27G 19/06 for band or strap 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 3/14 the means being photocells or other devices sensitive without mechanical contact
• CPC Class Codes: F16P 3/148 using capacitive technology
• CPC Class Codes: G05B 9/02 electric
• 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 83/088 Responsive to tool detector or work-feed-means detector
• CPC Class Codes: Y10T 83/089 Responsive to tool characteristic
• CPC Class Codes: Y10T 83/091 Responsive to work sensing means
• CPC Class Codes: Y10T 83/141 With means to monitor and control operation [e.g., self-regulating 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
• CPC Class Codes: Y10T 83/541 : Actuation of tool controlled in response to work-sensing means
• CPC Class Codes: Y10T 83/613 : Work guard
• CPC Class Codes: Y10T 83/7693 : Tool moved relative to work-support during cutting
• CPC Class Codes: Y10T 83/7697 : Tool angularly adjustable relative to work-support
• CPC Class Codes: Y10T 83/7726 : By movement of the tool
• CPC Class Codes: Y10T 83/7734 : With guard for tool
• CPC Class Codes: Y10T 83/7788 : Tool carrier oscillated or rotated
• CPC Class Codes: Y10T 83/85 : Signal; e.g., alarm
• CPC Class Codes: Y10T 83/8773 : Bevel or miter cut

Abstract

Woodworking machines including conductive cutters adapted to cut workpieces, and motors adapted to drive the cutters are disclosed. The machines also include a contact detection system adapted to detect contact between a person and the cutter, and to distinguish contact between the person and the cutter from contact between the workpiece and the cutter. The machines further include a reaction system adapted to cause a predetermined action to take place upon detection of contact between the person and the cutter by the contact detection system.

Claims

1. A woodworking machine comprising:

a support structure;

a motor supported by the support structure;

a blade assembly including a blade with cutting teeth, where the blade assembly is supported by the support structure and moveable by the motor, and where the blade assembly is electrically isolated from the support structure;

a reaction system adapted to perform an action to mitigate injury if a person contacts the blade; and

a contact detection system to detect contact between the blade assembly and a person, where the contact detection system includes circuitry adapted to generate a drive signal, to apply the drive signal to the blade assembly, and to detect a change in the electrical signal on the blade assembly due to an electrical load applied to the blade assembly, where the contact detection system is adapted to trigger the reaction system when the electrical load applied to the blade assembly is sufficient to lower the electrical signal on the blade assembly to a predetermined amplitude over a predetermined period of time, and where the contact detection system is further adapted to adjust the drive signal to try and maintain a predetermined electrical signal amplitude on the blade assembly in the presence of changing electrical load applied to the blade assembly by cutting wet wood.

2. The machine of claim 1 where the electrical load on the blade assembly sufficient to lower the electrical signal to the predetermined level over the predetermined period of time corresponds to a threshold electrical load, and where the threshold electrical load adjusts with the drive Signal.

3. The machine of claim 1 where the electrical load on the blade assembly sufficient to lower the electrical signal to the predetermined level over the predetermined period of time corresponds to a threshold electrical load, and where a higher threshold electrical load is required to trigger the reaction system when cutting-wet wood than when cutting dry wood due to the drive signal increasing to compensate for the electrical load on the blade assembly due to the wet wood.

4. The machine of claim 1 where the predetermined amplitude is such that the electrical load applied to the blade assembly by cutting wet wood is sufficient to lower the electrical signal on the blade assembly to the predetermined amplitude but not over the predetermined period of time.