Composite agitator

Abstract

A mixing agitator, for industrial use in mixing processes, that overcomes disadvantages associated with glass coated mixing agitators in the prior art. In particular, the mixing agitator includes a glass coated metal hub radially symmetrical about a central axis. The hub is at least partially embedded within a fluorinated polymer. The fluorinated polymer extends beyond the hub and forms agitator blades that may be reinforced. The hub has a centrally located receiving portion for receiving a drive shaft for rotating the agitator. The agitator is lighter weight than prior art glass coated steel agitators yet still has excellent chemical resistance and good temperature resistance. The agitator of the invention reduces likelihood of glass damage and permits agitator blade shapes not useable by glass coated agitators in the prior art. The invention also includes a mixing apparatus incorporating the hub and a method for mixing using the agitator.

Claims

1. A mixing agitator that is a rotating portion of a mixer having blades that cause mixing turbulence which blades comprise fluorinated polymer and have sufficient strength to withstand mixing forces when rotated in a fluid other than gas, said mixing agitator further comprising a glass coated metal hub radially symmetrical about a central axis; wherein said hub is partially embedded within the fluorinated polymer and the fluorinated polymer is secured to the hub by securing portions of the hub, said fluorinated polymer extending beyond said hub and forms said agitator blades, said glass coated metal hub having a centrally located receiving portion about the central axis for receiving a drive shaft for rotating the agitator.

2. The mixing agitator of claim 1; wherein the fluorinated polymer is polytetrafluoroethylene (PTFE).

3. The mixing agitator of claim 2; wherein the metal is steel or an iron alloy.

4. The mixing agitator of claim 2; wherein the metal is an alloy of titanium, vanadium, chromium, nickel, iron, zirconium or mixtures thereof.

5. The mixing agitator of claim 1; wherein the fluorinated polymer comprises embedded reinforcement.

6. The mixing agitator of claim 5; wherein the reinforcement comprises embedded carbon, glass, metal, or ceramic.

7. The mixing agitator of claim 6 where the reinforcement comprises embedded carbon fiber, glass fiber or metal fiber.

8. The mixing agitator of claim 7; wherein the embedded fiber is steel fiber.

9. The mixing agitator of claim 1; wherein the receiving portion is a hole having a ground glass sidewall.

10. The mixing agitator of claim 1; wherein the hub comprises securing portions surrounded by the fluorinated polymer, such that the fluorinated polymer can't be removed and the securing portions assist in stabilizing the agitator blades.

11. The mixing agitator of claim 1; wherein the fluoropolymer is fused about the hub to embed at least a portion thereof.

12. A mixing apparatus; wherein it comprises the agitator of claim 1 connected to the drive shaft at the receiving portion and a rotational drive connected to the drive shaft.

13. The mixing apparatus of claim 12; wherein the fluorinated polymer comprises embedded reinforcement in the form of embedded carbon fiber, glass fiber or metal fiber and the receiving portion in the hub comprises a hole having a ground glass sidewall and where the drive shaft is glass coated and has a ground glass end for mating with the hole in the hub.

14. The mixing apparatus of claim 13; wherein the drive shaft and hub are connected by an interference fit.

15. A method for mixing substances; wherein it comprises mixing in the apparatus according to claim 12.

16. A mixing agitator that is a rotating portion of a mixer having blades that cause mixing turbulence which blades comprise fluorinated polymer and have sufficient strength to withstand mixing forces when rotated in a fluid other than gas, said mixing agitator further comprising a glass coated metal hub radially symmetrical about a central axis; wherein said hub is partially embedded within the fluorinated polymer and the fluorinated polymer is secured to the hub by securing portions of the hub, said fluorinated polymer extending beyond said hub and forms said agitator blades, said glass coated metal hub having a centrally located receiving portion about the central axis for receiving a drive shaft for rotating the agitator; wherein the hub comprises securing portions surrounded by the fluorinated polymer, such that the fluorinated polymer can't be removed and the securing portions assist in stabilizing the agitator blades; wherein the securing portions comprise fluorinated polymer embedded glass coated lugs.

17. The mixing agitator of claim 16; wherein the lugs each comprise a through hole filled with and securing the fluorinated polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a top perspective view of a first preferred embodiment of a mixing agitator of the invention.

(2) FIG. 2 is a top perspective view of a second preferred embodiment of a mixing agitator of the invention.

(3) FIG. 3 is a top perspective view of a third preferred embodiment of a mixing agitator of the invention.

(4) FIG. 4 is a top perspective view of a preferred embodiment of central hub of a mixing agitator of the invention.

(5) FIG. 5 is an elevational cross-sectional view of a preferred embodiment of a tank containing a mixing apparatus of the invention.

DESCRIPTION OF THE EMBODIMENTS

(6) As used herein, “agitator” is intended to mean the rotating portion of a mixer having blades, or the equivalent, that cause mixing turbulence. Such agitators have also been historically referred to in the art as turbines or impellers.

(7) The invention is a mixing agitator that overcomes or reduces disadvantages associated with glass coated mixing agitators in the prior art as discussed in the Background of the invention.

(8) In particular, the blades of the agitator of the invention, being made of fluorinated polymer, eliminates the problem concerning damage at corners and edges of glass coated blades. In accordance with the invention, blades can thus be made with shapes, sharp edges and corners, while retaining other advantages of glass coated glass coated agitators including chemical resistance and good heat resistance.

(9) In addition, the agitator weight is dramatically reduced thus requiring less energy input to cause the agitator to reach a desired high speed and to reach a desired speed in less time, while at the same reducing kinetic energy in the agitator resulting in easier control. In addition, the weight of the agitator is less than a traditional glass coated steel agitator making it easier to assemble. Further, the huge centrifugal forces developed due to the high mass of glass coated mixing agitators, that increase structural requirements, are eliminated.

(10) In accordance with the invention, problems associated with plastic agitators have been reduced or eliminated. Fluorinated polymers can have good chemical and heat resistance but their strength was previously insufficient. In accordance with the invention, this has been addressed in at least three ways. In accordance with the invention, the fluoropolymer can be reinforced, the hub, where large stress of attachment to the drive shaft occur, has been retained in the form of a glass coated steel hub, and securing the fluoropolymer to the hub has been accomplished by providing securing portions, e.g. lugs with at least one hole, so that the fluoropolymer grabs the hub when the hub is embedded.

(11) The fluoropolymer is preferably polytetrafluoroethylene (PTFE) often referred to by the trademark of Chemours as TEFLON®. Although commonly cost prohibitive and without the temperature and chemical resistance combination of PTFE, other fluorinated polymers may be used, e.g. fluorinated ethylene propylene (FEP); ethylene-trifluoroethylene (ECTFE); polyethylene-tetrafluoroethylene (ETFE); and PTFE modified with a small amount of perfluoroalkoxy co-monomer, known as (PTFM). Due to the small amount of modification, PTFM is also commonly referred to as PTFE.

(12) In using PTFE in accordance with the invention, PTFE powder is usually fused over almost all of the hub, except the center, to form the desired agitator shape. Occasional machining may; however, be used. Agitator blades can thus be made in any desired shape, e.g. straight, curved, compound curved, and angled at almost any degree and with sharp or rounded edges and corners. The blades do, however have a base at the hub and extend generally radially outward in straight. angled or curved orientations.

(13) The metal under the glass in the glass coated hub is usually steel but for security and/or weight may be a chemically resistant metal such as titanium, vanadium, chromium, nickel, iron, zirconium or alloys or mixtures thereof. The metal is commonly an alloy of iron. The same metals may be used in the glass coated drive shaft.

(14) Embedded reinforcement in the fluoropolymer may, for example, be carbon, glass, metal or ceramic and may be in the form of aggregate or fiber. Fiber is preferred and may be individual fibers or woven fibers, e.g. in the form of cloth. The metal may be steel fiber.

(15) The receiving portion of the hub is preferably a hole having a ground glass sidewall designed to mate with a ground glass end of the drive shaft. In attaching the shaft, the shaft may be hollow so that a cryogenic fluid, e.g. liquid nitrogen, can be poured into an open top of the shaft so that is flows to the bottom where the cooling cause constriction at the ground glass end. When the constricted end is introduced into the receiving portion of the hub and the fluid evaporates, the end of the shaft expands and locks onto the hub.

(16) The securing portions of the hub for securing and stabilizing the agitator blades can be any arrangement that can be surrounded by the fluorinated polymer such that it can't be removed, e.g. opposing grooves or holes through a structure that will fill with the fluoropolymer The securing portions may include glass coated lugs. A preferred structure is a lug with one or more holes that are filled with fluoropolymer that is contiguous with fluoropolymer on opposing surfaces.

(17) The invention also includes a mixing apparatus (machine) where the agitator is connected to a drive shaft as previously described and has an end connected to a drive that is usually an electric motor but may be a hydraulic or driven rotational motor or a belt or chain connected to another rotating device such as a water, steam or gas turbine.

(18) The invention may be further understood by reference to the drawings as discussed below which illustrate preferred embodiment best modes of the invention contemplated by the applicant.

(19) FIGS. 1, 2 and 3 show mixing agitators. 10a, 10b and 10c in accordance with the invention each having a glass coated metal hub 12 radially symmetrical about a central rotational axis 14 partially embedded within a fluoropolymer 16 radially extending beyond the hub 12 in the form of agitator blades 18. Fluoropolymer 16 contains reinforcing fibers 20 and aggregate 22.

(20) The hub 12 has a centrally located receiving portion 24 about central axis 14 in the form of a hole having a ground glass sidewall 26 for receiving a ground glass end 28 of a glass coated drive shaft 30 (see FIG. 5), for rotating agitator 10. Hub 12 comprises securing portions 32 for securing and stabilizing the agitator blades 18. As shown in the embodiments in FIGS. 4 and 5, the securing portions 32 are in the form of lugs 34 having a through hole 36 filled with fluoropolymer 16 contiguous with fluoropolymer 16 embedding the hub 12 to stabilize fluoropolymer 16 and blades 18 relative to hub 12.

(21) As shown in FIG. 5, the invention also includes a mixing apparatus 38 including agitator 10 connected to drive shaft 30 at receiving portion 24 and a rotational drive 40 connected to drive shaft 30 for rotating the drive shaft 30 and thus rotating agitator 10. Mixing apparatus 38 is shown in conjunction with a glass coated metal container 42 in FIG. 5.

INDUSTRIAL APPLICABILITY

(22) The invention is a mixing agitator to mix materials in industry such that disadvantages associated with glass coated mixing agitators in the prior art are overcome or reduced.