Apparatus and method for singulating sheets and inserting same into envelopes

An apparatus for singulating individual sheets of film from a stack of sheets and transporting them to a conveyor, comprising:

• a. an elongated picker arm having an upper end and a lower end, said arm being pivotally mounted at said upper end for rotation in reciprocating fashion from a first position, in which said lower end is adjacent the stack, to a second position, in which said lower end is adjacent the conveyor;
• b. a foot extending from said lower end of said arm;
• c. a gripper jaw pivotally mounted to said lower end of said arm, said jaw having a bite portion;
• d. reciprocating means for rotating said arm alternatively between said first position and said second position;
• e. means for segregating a single sheet of film from the stack, and directing an edge of the segregated sheet toward said gripper jaw;
• f. drive means for closing said gripper jaw while grasping the edge of the segregated sheet of film between said bite portion and said foot with said arm in said first position, and for opening said gripper jaw with said arm in said second position;
• g. sensor means in said foot, for detecting the distance between said bite portion of said jaw and said foot after said edge is grasped, the distance corresponding to a thickness of the segregated sheet;
• and,
• h. means responsive to said sensor means, for comparing the sensed distance to a stored thickness value, and making a determination whether a fault condition exists.

A method for singulating sheets from a stack of sheets and depositing individual ones of them to a conveyor, comprising:

• a. establishing a normalized sheet thickness value and storing it as a digital number;
• b. segregating at least an edge portion of a lowermost sheet from the stack, and maintaining the edge in spaced relation from the stack;
• c. seizing the edge of the sheet between a gripping jaw and a foot;
• d. determining the thickness of the sheet using a sensor in said foot and storing the thickness as a digital number;
• e. comparing the thickness of the sheet to said normalized sheet thickness value and making a determination whether the sheet falls within a predetermined tolerance range, extending above and below said normalized sheet thickness value;
• f. marking the sheet for ejection if the thickness of the sheet falls outside said tolerance range;
• g. drawing the sheet away from the stack and depositing the sheet upon a conveyor;
• and,
• h. ejecting the sheet from the conveyor if the sheet is marked for ejection.

A method for detecting a fault condition during a picking cycle during which a picker arm having a gripper jaw and a foot grasps an individual sheet from a stack of sheets and transports the sheet to a conveyor, comprising the steps of:

• a. establishing a stored thickness value in digital form, said value corresponding to the normal thickness of a sheet to be grasped during the picking cycle;
• b. grasping an individual sheet from the stack;
• c. measuring a thickness for the individual sheet using a sensor in the foot and storing the measured thickness in digital form;
• d. determining whether said measured thickness is greater or less than the product of a predetermined factor times said stored thickness value, and marking the sheet for ejection, if said measured thickness is greater.

A method for initializing an apparatus for singulating sheets from a stack of sheets and transporting individual ones of them to a conveyor, comprising:

• a. seizing an edge of a sample sheet from the stack, between a gripping jaw and a foot;
• b. determining the thickness of the sample sheet by measuring the distance between said jaw and said foot using a Hall-effect sensor in said foot;
• and,
• c. storing the thickness of the sample sheet as a stored thickness value.