Aerated Powder Pump

Abstract

A pump for handling dry powdered material and including a stator forming a pump chamber, a rotor within the chamber and having an external helical fin thereon, the chamber having a material inlet and an outlet and gas inlet means at spaced intervals along the stator for injecting pressurized gas into the chamber, whereby the powdered material is aerated as the material moves through the chamber from the inlet to the outlet. The internal wall of the stator is preferably provided with a coating of polytetrafluoroetylene to minimize adhesion of the material to the stator wall.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an aerated pump and more particularly, it pertains to a system for pumping and spraying powdered resin.

2. Description of the Prior Art

Handling certain powdered materials such as flour, powdered metals, clay, and certain resins has been satisfactory where the material is pumped through a totally enclosed system of pipes. Such materials may be pumped in a so-called "progressive cavity" pump similar to that disclosed in U.S. Pat. No. 3,280,753, in which a metal rotor is in engagement with a stator composed of flexible resilient material such as rubber.

Where the powdered material being pumped is composed of a blend of certain resins and of a catalyst or curing agent, a problem arises. It has been found that with such a blend of powdered materials, the progressive cavity pump is practically useless, (particularly at higher speeds), because the metal rotor creates friction with a rubber stator and the heat created by the friction causes the catalyst or curing agent to set up and harden the powdered resin in the blend, thereby causing the pump to become inoperative.

SUMMARY OF THE INVENTION

In accordance with this invention it has been found that the foregoing problem may be overcome by providing the pump stator having an elongated cylindrical chamber and having a powder inlet and a powder outlet, the inner walls of the chamber being composed of a minimal friction material, a rotor within the pump chamber having a helical fin extending to the inner surface of the stator, gas injection means at spaced intervals along the length of the stator for injecting powder-fluidizing gas into the chamber, and additional air injection means on the side of the powder outlet remote from the chamber for moving the powder through the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view showing the pump; and

FIG. 2 is an enlarged sectional view showing the pump stator, rotor, and powder outlet end of the stator.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The apparatus of the present invention is a pump assembly generally indicated at 10 in FIG. 1. It includes a hopper 12, a pump 14, and a variable speed motor 16. The exit end of the pump is preferably provided with a hose 18, the outer end of which is provided with a spray nozzle 20.

As shown more particularly in FIG. 2, the pump 14 is an elongated cylindrical member having an outer casing 22 which together with an inner lining 24 forms a stator for a pump rotor 26. The rotor, which is propelled by the motor 16 through a shaft 28, is provided with a helical fin 30 so that the rotor 26 functions in a manner similar to an auger. The outer peripheral portion of the fin 30 extends to and contacts the inner surface of the lining 24. The rotor and fin may be composed of any rigid material. Such material may include a metal and is preferably composed of steel.

The right end portion of the rotor 26 is journaled in a brass collar 32 and includes a flange 34 to prevent longitudinal thrust of the rotor 26. The brass collar 32 is seated within the open end portion of the casing 22 where it is retained by a closure 36. A sealing collar 38 is disposed between the collar 32 and the inner liner 24.

The opposite end of the rotor 26 is journaled in a collar 40 which is preferably composed of a low adhesion material such as polytetrafluoroethylene. The collar 40 is disposed in a mounting member or spider 42, which is located within the outlet end of the pump 10 where it is retained in place by an adapter 44. A central bore 46 of the adaptor 44 communicates with the chamber of the pump 14. The end of the bore 46, remote from the spider 42, is provided with a check valve 48 which is pivotally mounted at 50 to permit the flow of powdered material to the left (as viewed in FIG. 2) and to prevent the reverse flow of the material into the pump stator. For that purpose the valve 48 swings clockwise to an open (broken line) position 48a when sufficient pressure within the pump chamber is maintained. However, when pressure in the pump chamber drops below the pressure on the left side of the valve, the valve 48 moves counterclockwise to the closed (solid line) position.

The adaptor 44 is composed of a material having a low coefficient of adhesion such as polytetrafluoroethylene. The exit end of the adaptor 44 is connected to a member 52 having a funnel-like inner surface 54 and having a threaded end portion 56 to which the hose 18 is connected. The member 52 may be composed of metal or of a material having a low coefficient of low adhesion such as polytetrafluoroethylene.

The pump assembly 10 including the hopper 12, the pump 14, the hose 18, and the spray nozzle 20 also includes means for aerating with air or other gas to circulate through the several parts for the purpose of "fluffing" or fluidizing the blended resinous material as it passes through the pump assembly. The aerating means includes a source of pressurized air (not shown) or other gas (such as nitrogen) which is innocuous to the materials comprising the resinous powder. The pressure is maintained at about 4 pounds per square inch and the gas is applied at strategic areas throughout the pump assembly 10 through several spaced nozzles. The nozzles include a nozzle 56 near the lower end of the fluidizing hopper 12, a nozzle 58 at the right end of the pump 14, and a plurality (for example) three nozzles 60 (FIG. 1) at spaced intervals along the pump 14. Another nozzle 62 is provided in the adaptor 44 and communicates with the central bore 46. Still another nozzle 64 is provided in the member 52 where it communicates with the chamber formed by the surface 54. All of the nozzles 56 to 62 are connected by similar gas conduits 66 to the common source of gas pressure. Accordingly, a gas is applied throughout the assembly so as to provide a continuous aerating condition to the powdered resinous material as it passes through the pump, and thereby prevent the powdered material from depositing and accumulating within the pump.

As the resinous material passes from the hopper into the rotor chamber of the pump 14 and then through the spider 42 having openings 68 into the bore 46, and thence through the member 52 into the hose, the gas entering the assembly maintains the resinous material in a substantially fluidized state.

A typical example of the resinous powder may include a blend of two solid epoxy resins, a yellow pigment, an amine curing agent or catalyst, and a silica filler.

The several parts including the inner pump lining 24, the collar 40, the adaptor 44, and the check valve 48, being composed of a material having a low adhesion coefficient such as polytetrafluoroethylene, contribute to the overall effect of preventing adherence of the resinous material to the surfaces of the pump. More particularly, the lining 24 provides a minimum of frictional resistance to the resinous powder as it is propelled through the pump chamber. The lining 24 prevents the creation of any hot spots between the helical fin 30 and the stator which would otherwise cause the curing agent or catalyst, constituting part of the resinous powder, from setting up and hardening, causing ultimate pump failure.

The nozzle 64 normally functions with the other nozzles 56 to 62 to fluidize the resinous powder as it passes through the member 52. The nozzle 64 however is connected to a conduit 70 which is maintained in operation for some time, such as upwards for one minute, after shutdown of the rest of the pump 10 in order to blow all of the resinous powder out of the member 52, the hose 18, and the nozzle 20. During the blowing out period after the pump is shut down, the check valve 48 returns to the closed (solid line) position, whereby air entering the member 52 via the nozzle 64 is prevented from blowing resinous material back into the bore 46 and the pump chamber.

Accordingly, the several air injection nozzles 56-64 cooperate with the rotor 26 and the several parts including the lining 24 to prevent the resinous powder from depositing and packing anywhere in the pump and particularly at the outlet end thereof as the powder is directed into the hose and out of the manually operated nozzle 20. The pump is adapted to move about 1 pound of resinous powder in 1 minute, and has an average output of about 6 pounds in 10 minutes.

It is understood that the above specification and drawings are merely exemplary and not in limitation of the invention.

Claims

What is claimed is:

1. An apparatus for propelling a dry powdered resinous material comprising

1. an elongated cylindrical stator chamber having internal walls and a powdered material inlet and outlet;

2. rotor means of uniform diameter within said chamber for propelling said material from said inlet to said outlet;

3. a liner lining the walls of said chamber, said liner being of a material having a low coefficient of friction, and said liner being interposed between said rotor means and said chamber walls so as to prevent all contact between said rotor means and said chamber walls;

4. gas injection means along the walls of said chamber for introducing gas into said chamber for maintaining said material in a fluidized state;

5. a check valve at the outlet end of said chamber for preventing the reverse flow of said material;

6. a fitting attached to said chamber over said outlet; and

7. gas injection means for introducing gas into said fitting.

2. The apparatus of claim 1 wherein a bearing of a material having a low coefficient of friction supports said rotor means at said outlet.

3. The apparatus of claim 2 wherein said bearing material is polytetrafluoroethylene.

4. The apparatus of claim 1 wherein the lining is composed of polytetrafluoroethylene.

5. The apparatus of claim 1 wherein the rotor means is a rotatable shaft having a helical fin extending to the lining of the chamber walls.