General Signal Corporation

Keith T McDermott

Ronald J Weetman

Ronald N Salzman

Robert A Blakley

Marlin D Schutte

Chandler K Coyle

Jerry A Carpenter

Roger N Voss

Mixer apparatus having an impeller on a shaft, which circulates a body of liquid the surface of which can clear the impeller, especially when the liquid is in a tank, and the tank is drained, is protected against excessive by use of a flexural member, which may be in the form of radially opposed pairs of resilient plates, which extend from the shaft and are attached thereto by a collar. As the liquid surface drops below the impeller, the members present surfaces to the liquid in the tank on which forces are opposing the oscillation are developed by interaction of the surfaces with the liquid in the tank. Restoring forces on the shaft due to the flexing of the resilient plates also reduce the shaft oscillation. The stiffness of the plates is selected to optimize the restoring forces for the mixing apparatus which is stabilized.

Apparatus for stabilizing a mixer which circulates liquid against

A mixing process may be carried out in a tank of a certain diameter. The process may also be constrained to the use of an impeller of certain diameter in order to obtain the flow pattern desired to carry out the process. The power consumption of the system which may be expressed in terms of flow per unit (Q/P) is optimized for the impeller diameter to tank diameter (D/T) constraint by utilizing an axial flow blade, preferably having camber and a tip chord angle at the tip and an angle near the attachment to the shaft (the hub) which rotates the impeller, where the tip chord angle and the twist the difference between the blade angle (between the chord and a plane perpendicular to the axis of rotation of the shaft between the tip and hub) are varied in opposite senses; for example, increasing the tip chord angle to provide a more D/T for a more optimum Q/P to which the process is constrained and then reducing the twist to maintain the power efficiency at the higher tip chord angle. The freedom to increase the tip chord angle and reduce the twist provides flexibility enabling the use of a limited number, say three, of hubs, thereby reducing the cost of the impeller system. The efficiency of the impeller is further increased by reducing tip vortices using slots in the tip which have an effect on the flow pattern similar to the effect of proplets but at reduced cost of fabrication. Where additional turbulence is required so as to establish shear forces in the fluid or fluid suspension being mixed, the blade segments which define the slots may be twisted at angles different from the tip chord angle. These twisted segments increase turbulence and shear the material being mixed.

Mixing impellers and impeller systems for mixing and blending liquids

A method for making an end connection for a shaft made of composite material, which accommodates for differences in stiffness, thermal expansion, and chemical resistance between the shaft and the member connected thereto and operates under oscillating torque, thrust, and bending loads, and also provides for manufacturing flexibility in enabling the shaft and connection to be produced as separate parts which are formed when final assembly is to occur. The connection has a male insert which is inserted into the end of the composite shaft. Axial and circumferential grooves are cut in the surfaces of the male insert and the shaft. These grooves are aligned to form circumferential and axial keyways which intersect each other. Material is injected into the keyway and polymerizes to form structural keys which transmit the thrust and torque, while locking the insert member and the shaft permanently together. The bending loads are transmitted through the tight fit extending axially between the composite shaft, insert member and keys. The radial thickness of the end of the shaft, the amount and orientation of the reinforcing fibers therein and the insert are matched so that their stiffness index approximately match. The composite shaft may be connected to a mixing impeller to provide a reliable support and drive therefor.

Method for making an end connection for composite shafts

An end connection for a shaft made of composite material, which accommodates for differences in stiffness, thermal expansion, chemical resistance between the shaft and the member connected thereto and operates under oscillating torque, thrust, and bending loads, and also provides for manufacturing flexibility in enabling the shaft and connection to be produced as separate parts which are formed when final assembly is to occur. The connection has a male insert which is inserted into the end of the composite shaft. Axial and circumferential grooves in the surfaces of the male insert and the shaft. These grooves are aligned to form circumferential and axial keyways which intersect each other. Material is injected into the keyway and polymerizes to form structural keys which transmit the thrust and torque, while locking the insert member and the shaft permanently together. The bending loads are transmitted through the tight fit extending axially between the shaft, insert member and keys. The radial thickness of the end of the shaft, the amount and orientation of the reinforcing fibers therein and the insert are matched so that their stiffness index approximately match. The composite shaft may be connected to a mixing impeller to provide a reliable support and drive therefor.

End connection for composite shafts

Apparatus for mixing liquid and liquid suspension mediums in vessels with a mixing impeller shaft system of a composite of fibrous and plastic material of a structural configuration to enable the use of such material in commercial and industrial applications where the reaction loads of the medium on the system militate against the use of composite fibrous and plastic material. The system utilizes impellers having blades which distribute the reaction load through a hub on a mounting area of a shaft with keys and keyways in a manner to avoid stress risers unamicable to the composite material and which can cause failure thereof. Separate keys and keyways are provided to oppose the thrust due to the reaction loads and to oppose the torque due to such loads. Plural thrust keyways may be used to enable the impeller to be located at different positions on the shaft and at selected heights above the floor of the mixing vessel. Proplets on the tips of the blades extend entirely in the direction of the low pressure surface of the blades to control the flow field in the vessel and provide a more axial velocity profile of the inlet flow to the impeller which is nearly axial and substantially reduces the strength of the tip vortices.

Mixing apparatus

Mixing systems for liquids having fibers suspended therein wherein the fibers tenaciously adhere to and accumulate on the leading edge of the impeller, thereby increasing the drag of the liquid on the impeller as it rotates and the consequent increase in the power required to rotate the impeller. Axial flow of the liquid in a tank is produced by the impeller within a draft tube. The leading edge of the blades of the impeller are inclined with respect to radial lines extending from the axis of rotation of the impeller beyond the angle of repose of the fibers on the leading edge. Also, the coefficient of friction of the portion of the impeller, extending from the leading edge toward the trailing edge thereof, to which the fibers adhere is reduced by providing the surface thereof with a low coefficient of friction material.

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Rochester, NY, United States of America

Keith T McDermott