Two-stage screw auger pumping apparatus

A pumping apparatus, comprising:

• a pump housing defining a material infeed opening, and at least one material discharge opening;
• a pair of auger means extending within said pump housing, each said auger means including helical flight means intermeshed with the flight means of the other auger means, said pair of auger means being rotatable together about respective parallel axes for moving material through said housing generally axially of said auger means from said material infeed opening downstream to said material discharge opening, each of said auger means having a free, upstream end,
• each said auger means comprising a core outwardly from which the respective flight means extends, each said auger core including at least a portion which is generally tapered and increasing in diameter in a direction corresponding to the direction movement of material through aid pump housing,
• each said flight means including first-stage flight means intermeshed with the first-stage flight means of the other auger means, and second-stage flight means intermeshed with the second-stage flight means of the other auger means,
• said pump housing being configured to define said infeed opening in an orientation for gravity infeed of material into the pumping apparatus in a direction generally axially of said pair of auger means, said infeed opening being aligned with the parallel axes of said pair of auger means so that material moving through said infeed opening moves substantially along said parallel axes, said infeed opening being dimensioned substantially at least large as the upstream end projection of said pair of auger means, and
• means for rotatably driving said pair of auger means operatively connected with said auger means generally at the downstream ends thereof for driving said auger means independently of said intermeshed flight means, whereby said pair of auger means provides a two-stage pumping action within said housing, including a first, upstream non-positive displacement pumping provided by said intermeshed first-stage flight means, and a second, downstream positive displacement pumping provided by said intermeshed second-stage flight means, said first stage flight means acting to create a net positive suction at an interface of said first and second stage flight means.

A method for flowing difficulty flowable material which comprises introducing said material into an infeed opening of a housing having infeed and discharge openings generally at ends, and thereby bringing said material into contact with free, upstream ends of a pair of counter-rotating auger means including respective, intermeshed helical flight means including a pair of intermeshed first stage flight means and a pair of intermeshed second stage flight means, wherein said pair of auger means are rotatably driven generally at downstream ends thereof independently of the respective, intermeshed flight means, and wherein said infeed opening is oriented for gravity infeed of the material into said housing in a direction generally axially of and in alignment with the rotational axes of said flight means, moving said material through a first pumping zone by the action of said first stage flight means of said helical flight means by non-positive displacement pumping, and thereafter moving said material into and through a second pumping zone by the action of said second stage flight means of said helical flight means by positive displacement pumping, including creating a net positive suction head at an interface of said pumping zones by the action of said first flight means, and moving said material through said interface in a direction substantially parallel to said rotational axes to promote streamlined flow of said material, and thereafter discharging said material through said discharge opening.