Positive drive helical conveyor system

A conveyor system comprising an endless flat belt having a plurality of links connected together by a plurality of transverse rods and adapted for alternate collapse and expansion relative to said rods along at least one edge of said belt to permit passage of the belt around lateral curves, with said rods extending radially in said curves, said rods having heads protruding from said links along said belt edge,

• means to support said belt for passage through an endless path including a helical portion extending through a plurality of vertically spaced loops with the belt curved laterally in each of said loops, an approach portion leading into the first loop at one end of said helical portion and an exit portion leading away from the last loop at the other end of said helical portion,
• primary drive means having drive surfaces engaging spaced ones of said rod heads in positive driving relationship at a plurality of circumferentially spaced places along a radially inner edge of said belt in each of said loops to positively drive said radially inner edge at the same speed as said driving surfaces, said rods transferring the driving force to the radially outer portions of said belt, said primary drive means including means at predetermined vertically spaced locations along said driving surfaces to effect controlled release of said positive driving engagement with the driven rod heads at said locations to permit said released positive driving engagement to be re-established with an adjoining rod head,
• secondary drive means synchronized with said primary drive means to maintain a substantially fixed length of belt extending between said one end and said other end of said helical portion to enable said belt to be positively driven smoothly through said loops by said primary drive means under substantially minimal tension and substantially minimal driving pressure exerted by said primary drive means.

A conveyor system comprising an endless flat belt having a plurality of links connected together and adapted for alternate collapse and expansion along at least one edge of said belt to permit passage of the belt around lateral curves, said belt having protrusions spaced along at least one edge thereof, each of said protrusions having a side surface and an end surface,

• means to support said belt for passage through an endless path including a helical portion extending through a plurality of vertically spaced circular loops with the belt curved laterally in each of said loops, with said protrusions on the radially inner edge thereof, a planar approach portion leading tangentially into the first loop at one end of said helical portion and a planar exit portion leading tangentially away from the last loop at the other end of said helical portion, guide means directing said belt into said planar approach portion,
• primary drive means comprising a cylindrical cage rotatable about a vertical axis and having a plurality of vertical driving bars spaced circumferentially around the cage, said bars having radial driving surfaces overlapping and abutting the side surfaces of at least some of said protrusions in positive driving relationship to positively drive said protrusions at the same speed as said driving surfaces and circumferential surfaces engaging the end surfaces of at least some of said protrusions to limit the overlapping of said bars and said protrusions to prevent substantial extraneous contact between said cage and said belt, said protrusions being slidable vertically along said bars whle said cage rotates to positively drive said belt, and secondary drive means synchronized with said primary drive means and positively engaging said belt at a first location along said planar approach portion closely adjacent said one end of said helical portion and at a second location along said planar exit portion closely adjacent said other end of said helical portion to cause the belt to travel at the same speed at said first and second locations, said secondary drive means having forwardly facing drive surfaces engaging said belt in forward driving relation and rearwardly facing retarding surfaces engaging said belt in rearward retarding relation while said belt moves in a planar path along said approach and exit portions, said first and second locations being positioned to maintain a substantially fixed length of belt extending between said one end and said other end of said helical portion to enable said belt to be positively driven smoothly through said loops by said cage under substantially minimal tension and substantially minimal driving pressure exerted by said cage,
• and means on said primary drive means at predetermined vertically spaced locations along said driving surfaces to effect controlled release of said positive driving engagement with the protrusions at said locations to permit said released positive driving engagement to be re-established with an adjoining protrusion.

A method of driving an endless flat belt along a path having a helical portion, a planar entrance portion and a planar exit portion which comprises steps of

• supporting said belt in a laterally curving orientation to form a plurality of vertically spaced generally horizontal loops in said helical portion with the radially inner edges of said belt in said loops defining substantially a cylinder,
• applying a positive primary driving force circumferentially of said cylinder to the radially inner edge of said belt at closely spaced places along said loops,
• selectively applying positive secondary driving and positive retarding forces substantially simultaneously to said belt at a first location along said planar portion closely adjacent the entrance end of said helical portion and at a second location along said planar exit portion closely adjacent the exit end of said helical portion to maintain a substantially constant length of the belt throughout said helical portion under substantially minimal longitudinal tension,
• retaining said positive driving force at each of said places of application for predetermined substantial circumferential distances along said loops,
• selectively effecting controlled release of said positive driving force at predetermined intervals from the respective places of application and reapplying the released positive driving force to adjoining places of application along said loops.