This is from the PTI patent. Figure 1 shows the blade retraction system under normal operating conditions. Figure 2 is a cutaway of the blade retraction mechanism. A cylinder (66) fits inside a cylinder bore (64). When the spinning blade touches flesh a capacitor sends a burst of high amperage electricity through a wire (78) and into a pin (74) that causes a .22 calibre cartridge (68) to fire.
Figure 3 shows the blade as it begins to retract after the cartridge is fired. Figure 4 shows the firing mechanism (60) at the same point in time: The gas generated the cartridge (68) has forced the cylinder (66) out of the bore (64) and driven the hammer (82) into an anvil (102 fig 3) that is a connected to a curved arm (20). The arm is connected to the saw’s arbor and is beginning to pull it below the table.
Figure 5 shows the position of the blade and arbor (16) when fully retracted. Note how the arm (18) that the arbor is attached to has pivoted away from the table and carried the blade with it.
The defendants listed on the first page of the complaint are a who’s who of power tool makers that sell table saws in the U.S. Chang Type Industrial owns Delta, having purchased it from SB&D in 2011. Emerson Electric is listed because it owns the Ridgid brand. It’s unclear why Milwaukee is there; it doesn’t even make table saws. Pentair, which sold its power tool business (Porter-Cable and Delta) to Black & Decker in 2004, has been released from the suit by the judge. Techtronic (TTi) is on the list because it owns Ryobi (and also Milwaukee).
This is from page 20 and 21 of the complaint filed by SawStop and SD3. What’s interesting is PTI’s estimate of the annual number of table saws shipped between 2006 and 2010. If those figures are correct, sales averaged 700,000 units per year. Multiply that by the licensing fee SawStop would receive if its technology was used on each of those saws (SawStop has said $50 each; PTI has said $200 ) and you can see why the two sides think this is worth fighting about.
Page 22 of the complaint contains the Consumer Product Safety Commission’s estimate of the annual cost of table saw injuries: $2.36 billion per year. It’s worth noting that this number includes the cost of medical treatment, lost work time, legal and administrative fees, AND the “pain and suffering” that would be awarded if every table saw injury resulted in a lawsuit and the injured party won. More to follow…
In 2012 PTI commented (see paragraph 3; page 21) on the CPSC’s proposed rule, stating that 80% of the estimated cost (ICM) of $2.36 billion per year is pain and suffering. According to PTI, the inclusion of legal fees and pain and suffering has caused the CPSC to overstate the cost to society of table saw injuries.