Conveyor system and method for assuring a continual backlog

A conveyor system which assures an adequate and continuous supply of conveyed items at the output thereof comprising:

• a supply conveyor means including a variable speed drive means for conveying said items at a variable rate;
• an accumulator conveyor means having an input communicating with the output of said supply conveyor, said accumulator conveyor means including accumulator drive means for conveying said items at a faster rate than any said variable rate of said supply conveyor;
• a retarder conveyor means including a retarder drive means having an input communicating with the output of said accumulator conveyor means, the speed of said retarder conveyor means being less than the speed of said accumulator conveyor means so as to permit a backlog of mutually abutting items to accumulate at said accumulator conveyor output without stopping said items at said accumulator conveyor output;
• a sensor means associated with said accumulator conveyor means for sensing the backlog of said accumulator conveyor means said sensor means comprising a series of uniformly spaced optical sensors extending along said accumulator conveyor means, said optical sensors having a maximum spacing substantially equal to the maximum dimension of said conveyed items in the direction of advance along said accumulator conveyor means so as to provide a signal representing a count of mutually abutting and mutually spaced conveyed items on said accumulator conveyor means regardless of the position of said items on said conveyor means relative to said optical sensors;
• and
• a variable speed control means having an input coupled to said sensor means and an output coupled to said variable speed drive means so as to control the speed of said supply conveyor means and the advancement of said conveyed items to said accumulator conveyor means in response to said signal representing said count so as to assure an adequate backlog at said accumulator conveyor output.

A conveyor system which assures an adequate and continuous supply of conveyed items at the output thereof comrpising:

• a supply conveyor means including a variable speed drive means for conveying said items at a variable rate;
• an accumulator conveyor means having an input communicating with the output of said supply conveyor, said accumulator conveyor means including accumulator drive means for conveying said items at a faster rate than any said variable rate of said supply conveyor;
• a retarder conveyor means including a retarder drive means having an input communicating with the output of said accumulator conveyor means, the speed of said retarder conveyor means being less than the speed of said accumulator conveyor means so as to permit a backlog of mutually abutting items to accumulate at said accumulator conveyor output without stopping said items at said accumulator conveyor output;
• a sensor means associated with said accumulator conveyor means for sensing the backlog of said accumulator conveyor means said sensor means comprising a series of uniformly spaced sensors extending along said accumulator conveyor means, said sensors having a maximum spacing substantially equal to the maximum dimension of said conveyed items in the direction of advance along said accumulator conveyor means so as to provide a signal representing a count of mutually abutting and mutually spaced conveyed items on said accumulator conveyor means regardless of the position of said items on said conveyor means relative to said sensors, said sensors having a sensing area measured in the direction of advance along said accumulator conveyor means substantially less than the maximum dimension of said conveyed items in the direction of advance along said accumulator conveyor means;
• and
• a variable speed control means having an input coupled to said sensor means and an output coupled to said variable speed drive means so as to control the speed of said supply conveyor means and the advancement of said conveyed items to said accumulator conveyor means in response to said signal representing said count so as to assure an adequate backlog at said accumulator conveyor output.