Patent ID: 7315007

Claim:
A method of preventing flat mail pieces having excessive thickness or stiffness from entering a mail processing machine wherein flat mail pieces are held on opposite sides and conveyed by paired conveyor belts around one or more curves, including one curve which is the sharpest curve in the mail processing machine, comprising the steps of: (a) conveying a singulated stream of flat mail pieces one at a time though a test curve upstream from the sharpest curve of the mail processing machine, the test curve including an angled section at which each mail piece tends to bend; (b) determining the thickness of each mail piece; (c) determining the stiffness of each mail piece by measuring deflection of one of the belts of the test curve as the mail piece is passing through the angled section, which deflection is in excess of deflection caused by the thickness of the mail piece as it passes between the belts; and (d) diverting a mail piece out of the mail processing machine before it reaches the sharpest curve of the mail processing machine if predetermined criteria are exceeded, the predetermined criteria including a maximum thickness, a maximum stiffness, and one or more combined stiffness and thickness values wherein the thickness is less than the maximum thickness and the stiffness is less than the maximum stiffness, wherein the angled section defines an angle less severe than the sharpest curve, whereby a mail piece that would jam the mail processing machine at the sharpest curve can pass through the test curve without jamming, and the predetermined stiffness and thickness criteria are based on a relationship between the test curve and the sharpest curve, which relationship is TH=D 2 *C, wherein TH is a combined stiffness/thickness value threshold of the sharpest curve, D 2 is the combined thickness and stiffness of a mail piece, and C is a multiplication factor which scales up the value of D 2 .