US3164420A

US3164420A - Bearing and seal

Info

Publication number: US3164420A
Application number: US227623A
Authority: US
Inventors: Jr Frank B Cramer
Original assignee: North American Aviation Corp
Current assignee: North American Aviation Corp
Priority date: 1959-12-04
Filing date: 1962-08-27
Publication date: 1965-01-05
Anticipated expiration: 1982-01-05

Description

Jan. 5, 1965 F. B. CRAMER, JR

BEARING AND SEAL 2 Sheets-Sheet 1 Original Filed Dec. 4, 1959 MIXED PRODUCT llll'i &4).

giwxik TTO NEY Jan. 5, 1965 I F. B. CRAMER, JR 3,164,420

BEARING AND SEAL Original Filed Dec. 4, '1959 2 Sheets-sheet 2 I A PI CGNSTITUENT CONSTITUENT DSSPERSION |2 MILL MXED PRODUCT INVENTOR. FRANK B. CRAMER JR.

AT RNEY United States Patent 3,164,420 BEARING AND SEAL Frank B. Cramer, Era, Reseda, Calif., assignor to North American Aviation, inc. Original application Dec. 4, 1959, Ser. No. 857,287. Divided and this application Aug. 27, 1962, Ser. No.

2 Claims. (Cl. 303-363) This is a division of application Serial No. 857,287, filed December 4, 1959.

This invention relates to an impeller-fed dispersion mill and more particularly to a dispersion mill which is capable of effectively mixing two or more preferably fluid or slurry type constituents of widely differing densities. By first partially mixing and accelerating the induced constituents by a novel propeller blade type chopping device and then subjecting the mixed constituents to a higher shear region of a colloid mill, a thoroughly mixed produce is produced. A typical application for the hereinafter described dispersion mill is set forth in the assignees Patent No. 3,022,149, issued February 20, 1962, and entitled, Process for Dispersing Solids in Polymeric Propellant Fuel Binders.

Conventional gravity feed systems employed by most dispersing devices, such as colloid mills and homogenizers, have been built on the assumption that they could be fed partially mixed materials and then proceed to increase the degree of dispersion. When such devices feed two or more liquids of widely different densities, for example, the more dense liquid tends to plug the intake port and further mixing is made difficult if not impossible. It the more dense liquid has an appreciably higher viscosity than either the mixture or the lighter liquid, the flow rate of the dispersing mill is greatly reduced.

The present invention overcomes the conventional feed systems by providing a continuous and uninterrupted dispersion wherein two constituents of unequal densities are fed separately into an initial chopping and accelerating blade type mixer and subsequently to the high shear regions of a colloid mill.

The main object of this invention is to provide an impeller-fed dispersion mill which will effectively mix two or more constituents of widely differing densities.

Another object of this invention is to provide a novel blade chopping means which will pre-mix constituents of varying densities which mixture is subsequently sub jected to the high shear regions of a colloid mill for the final mixing thereof.

A further object of this invention is to provide a novel seal arrangement for an impeller-fed dispersion mill.

These and other objects of the invention will become apparent from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 shows the impeller-fed dispersion mill of the instant invention.

FIG. 2 shows the novel seal arrangement used with the impeller-fed dispersion mill of FIG. 1.

FIG. 3 shows a schematic view of the mixing operation.

The impeller-fed dispersion mill of the present invention comprises two or more pipes which introduce constituents of varying densities to a pre-conditioner or blade type chopping and accelerating device which in turn feeds the partially mixed constituents to the high shear region of a colloid mill so as to effectively complete the mixing thereof. A novel seal arrangement is provided so that the rotating parts of the pre-mixer and colloid mills are free to rotate and the mixed constituents therein are effectively retained so that there is no danger of explosions due to the seeping of the mixed constituents into the friction creating moving parts of the mill.

Referring now more specifically to the drawings, FIG.

3,154,42 Patented Jan. 5, i965 1 discloses the impeller-fed dispersion mill wherein a housing 1 has inlet ports 2 and 3 formed therein adapted to be supplied with two preferably liquid or slurry type constituents by pump means, for example (FIG. 3). Althrough the preferred embodiment discloses only two inlet ports it is to be understood that any number of ports may be employed depending on the specific application thereof.

A rotatable shaft 4, adapted to be actuated by a conventional type motor, extends up through the housing and into the mixing chamber of the mill. On the upper extremity of the shaft, four staggered helical type blades 5 are fixedly secured to a bushing 6 which bushing is fixedly but removably secured to shaft 4 by a conventional slot and key type coupling, for example. It is to be noted that the blades 5 are so staggered and separated so that the leading and cutting edges 5a impart a chopping action to the constituents induced through inlets 2 and 3 when the shaft is rotated in a counter-clockwise direction as viewed in FIG. 1.

The cutting edges 5a of the four blades of the pre ferred embodiment illustrated in FIG. 1 are so constructed as to radially extend at approximately right angles with respect to the vertical axis of bushing 6 and approximately lie in the same vertical plane. The four cutting edges 5a are also shown circumferentially of and adjacent the upper surface of bushing 6 and approximately positionedninety degrees with respect to the adjacent cutting edge.

The blades 5 are helically formed on bushing 6 to extend downwardly in a spiral fashion and terminate adjacent the lower surface of bushing 6 so as to provide a ramp type passage.

The above construction alleviates the possibility of a fluid coupling, when fluid type constituents are utilized, between the constituents entering ports 2 and 3 and pro vides an effective chopping action thereto. It is to be further noted that the aforedescribed blade construction imparts a constant downward force to the constituents so as to provide a near positive feeding action.

Although FIG. 1 disploses four such staggered blades, it is to be understood that any desired number may be employed depending on the specific application.

Also removably fixed to shaft 4 by a conventional coupling are helical type gears 7 and 8 which cooperate with the helical type gear teeth 9 and 10 respectively, formed on the housing 1 and cooperate therewith to provide a high shear region for mixing constituents and at the same time allow passage therethrough. Propeller type blades 11 are connected to and radially project from shaft 4 at approximatly right angles to the longitudinal axis of shaft 4 to discharge the mixed product through outlet 12. The blades may be removably secured to a bushing similar in construction to bushing 6, if so desired. Although the illustrated embodiment of FIG. 1 discloses ten such blades, it is to be understood that any desired number may be employed to effectively discharge the mixed product for any specific application.

As disclosed in the preferred embodiment of FIG. 1, the rotatable shaft 4 is mounted on needle type bearings 13, although it is to be understood that the shaft 4 may be supported and rotated on any other type of conven tional bearings.

When the shaft 4 rotates there is a certain amount of friction and heat resulting therefrom. Accordingly, in the mixing of rocket motor propellants, it could prove very damaging to permit the highly combustible propellant materials being mixed in the mixing chamber to come in contact therewith.

To alleviate the possibility of the aforementioned contact, FIG. 2 discloses a positive seal 14 and a flushed seal 15 surrounding and cooperating with suitable shaft in the mixing chamber.

' flushed seal is constructed slightly loose on rotatable shaft 4.

An inlet port 16 formed in housing 1 is connected to a clearance formed of circumferential grooves 17a and passage 1% between rotatable shaft 4 and housing 1. A flushing material which is preferably identical with that of one of the constituents being induced into inlet 2 or 3 is induced into inlet port 16 and is free to flow into the mixing chamber of the mill. The pressure P in the inlet port 16 is regulated by conventional pump means, for example, so that it will be maintained at a greater pressure than that of P the pressure in An outlet port 18 is provided to i e-circulate the overflowing flushing constituents to inlet port 1o. A schematic showing of the aforedescribed construction is illustrated in FIG. 3.

From the above described construction, it is readily apparent that if it is desired to mix tWo constituents of difierent densities so as to form a polymer emulsion such as described in the above mentioned application, for example, the passage 16 is applied with one of the constituent liquids or slurry vehicles under a pressure P which pressure exceeds the pressure P in the mixing chamber. Consequently, a small continual flow of the constituent tends to flush the loose seal 15 and effectively prevents the lodging of oxidizer particles and/ or polymerizable materials at the seal shaft junction.

Such an arrangement provides for a real flushing agent which is not alien to the mixing constituents so as to cause contamination thereof. The utilization of one of .the liquid constituents as the flushing agent further makes possible the use of a non-positive type seal 15. The above described novel and seal arrangement also provides for the prevention of the washing out of the bearing lubrications at 13 thus assuring a safeguard against possible explosions.

Although the invention has been described and illustrated in detail, it is to be under tood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

I claim:

1. A sealing arrangement adapted to prevent the combustible mixed constituents of a propellant mixing mill from contacting friction creating surfaces comprising: a housing; a rotatable shaft mounted in said housing and rotatably mounted on hearing means adjacent said housing; first seal means encircling said shaft adjacent said bearing means and fixed to said housing so as to provide a near positive seal between said housing and said shaft; a second seal lying in a clearance formed in said housing, said second seal loosely encircling said shaft adjacent said first seal; an inlet-port formed in said housing and connected to said clearance; an outlet port formed in said housing and connected to said clearance; means adapted to supply a pressurized flushing agent identical to one of the mixed constituents to said clearance and said second seal, said means also adapted to recircuiate the agent to said inlet port.

2. A sealing arrangement adapted to prevent the combustible mixed constituents of a propellant mixing mill from contacting friction creating surfaces comprising:

a housing having an aperture,

a rotatable shaft situated within aid aperture,

first seal means encircling said shaft, said seal means providing a tight fit between said shaft and said housing, second seal means encircling said shaft adjacent said first seal, said second seal providing a loose fit on said shaft,

at least one circumferential groove formed in said housing encircling said shaft, said groove disposed between said inst and second seals,

an inlet port formed in said housing and connected to said groove,

an outlet port formed in said housing and connected to said groove,

whereby a pressurized fluid admitted through said inlet to said groove can flow about said shaft past said second but cannot flow past said first seal.

References Cited in the file of this patent UNi'iED STATES PATENTS 1,957,054 Waldorf May 3, 1934 2,714,045 Simenson July 26, 1955 2,857,144 Gurley Oct. 21, 1958

Claims

1. A SEALING ARRANGEMENT ADAPTED TO PREVENT THE COMBUSTIBLE MIXED CONSTITUENTS OF A PROPELLANT MIXING MILL FROM CONTACTING FRICTION CREATING SURFACES COMPRISING: A HOUSING; A ROTATABLE SHAFT MOUNTED IN SAID HOUSING AND ROTATABLY MOUNTED ON BEARING MEANS ADJACENT SAID HOUSING; FIRST SEAL MEANS ENCIRCLING SAID SHAFT ADJACENT SAID BEARING MEANS AND FIXED TO SAID HOUSING SO AS TO PROVIDE A NEAR POSITIVE SEAL BETWEEN SAID HOUSING AND SAID SHAFT; A SECOND SEAL LYING IN A CLEARANCE FORMED IN SAID HOUSING, SAID SECOND SEAL LOOSELY ENCIRCLING SAID SHAFT ADJACENT SAID FIRST SEAL; AN INLET PORT FORMED IN SAID HOUSING AND CONNECTED TO SAID CLEARACE; AN OUTLET PORT FORMED IN SAID HOUSING AND CONNECTED TO SAID CLEARANCE; MEANS ADAPTED TO SUPPLY A PRESSUIZED FLUSHING AGENT IDENTICAL TO ONE OF THE MIXED CONSTITUENTS TO SAID CLEARANCE AND SAID SECOND SEAL, SAID MEANS ALSO ADAPTED TO RECIRCULATE THE AGENT TO SAID INLET PORT.