US 2991051 A
Description (OCR text may contain errors)
July 4, 1961 D. w. JONES 2,991,051
AGITATOR PADDLE Filed Nov. 13, 1958 I no.4
DAVID W JONES Y INVENTOR:
it then falls. combined grit and vehicle flowing upon the lap is main- United States Patent 2,991,051 AGITATOR PAD-DUE J David W. Jones, Box 262, Cavecreek, Ariz.
Filed Nov. 13, 1958, Ser. No. 773,704 2 Claims. (Cl. 259-107) This invention relates to agitators for liquids carrying solids in suspension. It will be described with reference to its application to agitating lapping compounds, but it'is understood that the invention may be applied with equal facility to other liquids and compounds.
A production lapping machine has been devised in which a'flat annular lap is rotated under the work to be lapped, the work being held on the lap by suitable rotatable workholders supported against revolution with the lap. The actual abrading operation is performed by a grit which is held in suspension in a suitable liquid vehicle, the vehicle and grit suspended therein being allowed to fiow' or drip upon the rotating lap to maintain an appropriate quantity of usable grit on the lap. The grit and its vehicle are supplied from a container which may be mounted to one side of the lap and at a slight elevation therefrom so that with the aid of suitable valve means, the grit may flow from the containerdown a pipe, wire or 'other conductor into proximity with the lap upon which Uniformity in the composition of the tained by an agitator extending into the container and operated continuously while the machine is in use. f i It is customary to retain whatever lapping compound remains in the container at the end of a day, which means that overnight, while the agitator is not in operation, the g'rit'in the vehicle settles out. Where the machine is shut down at the end of the week, the settling out process may continue for two days so that when the machine is again about to be started, the lapping grit is in the form of a hard course, continued rotation of the paddle gradually breaks up all of the lumps and results in an even suspension of the grit in the liquid. The process of manually breaking up the settled out grit to enable the motor to turn the paddle is time consuming, and a thoughtless starting of the agitator motor without first loosening the settled out grit may result either in a broken paddle or a burnt out motor. I l 1 r.
The principal object of this invention is the provision of an agitator paddle which is capable of breaking up solidified matter settled around the paddle without the use of additional power to drive the paddle.
A more specific object of this invention contemplates the provision of an agitator paddle which is constructed to withdraw from the solidified matter settled around it, rather than to pass through it, and then to bear resiliently upon the solidified matter until the matter is completely eroded thereby and put into suspension.
As a further object, this invention has within its purview the provision of an agitator paddle which is resilient such that when confronted with settled out matter, it will bend and wind itself around the shaft on which it is mounted, thereby reducing the load on the drive motor for the shaft and making it possible for the motor to rotate the agitator until the resilient pressure of the agitator on the solidified matter has eroded the latter and placed it in suspension.
These and other objects of this invention will become apparent from the following detailed description thereof 2 when taken together with the accompanying drawings, in which:
FIG. 1 is a side elevational view in section of an illustrative container to which this invention may be applied; FIG. 2 is a plan view in section of the container of FIG. 1 showing the condition of the agitator when encountering settled out grit;
FIG. 3 is a plan view corresponding to FIG. 2 showing the agitator after it has put all of the settled out matter 1n suspension;
FIG. 4 is an enlarged elevational view of the agitator paddle and its drive shaft;
' FIG. 5 is a section through the shaft of FIG. 4 taken along line 5 5 and in the direction of the arrows at the ends thereof; and
FIG. 6 is an end elevation of the agitator paddle.
Referring now to the drawings for a detailed description of the invention and particularly to FIG. 1, there is shown a container 10 which, in the form illustrated, has a flat bottom wall 11, a cylindrical side Wall 12, with a radius 13 connecting the bottom and side walls. The open top 14 of the container is closed by a cover plate 15 on which are mounted a drive motor 16, an agitator shaft 17 extending downwardly into the container, and suitable reduction gearing 18 which transmits the drive from the motor 16 to the shaft 17.
Within container 10 is a lapping compound which normally is a liquid vehicle in which is suspended a lapping abrasive or grit in the form of a powder. For purposes of illustration, the lapping compound is shown in the condition in which it exists after a long period of inoperation of the agitator. The grit 19 has settled out at the bottom of the container and the relatively clear liquid 20 is above the grit.
It may be appreciated that the settled out grit is quite hard and that this condition tends to be aggravated by the passage of time. The grit will, of course, settle out around any agitator paddle which may be mounted on the end of shaft 17 so that the paddle is in effect locked in the hard grit. Normally, without the aid of the present invention, the agitator could not be turned by its driving motor without first having someone break up the settled out grit to reduce the load on the motor.
a In accordance with the present invention, the agitator paddle 21 is constructed to yield to tangential forces and to bend into the form of a spiral such that its radial dijmension is decreased until the resistance to turning is reduced to a value within the capacity of the motor 16 to handle. The paddle 21 is in efiect pulled inwardly along the channel 22 formed around it by the settled grit .grit with whichit is confronted. As it is being pulled inwardly, the front surface 23 is dragged along the adjacent wall 24 and erodes that surface to start the general breaking-up of the solidified grit '19. The force required to start the paddle moving inwardly being considerably less than that required to push the paddle through the settled grit, motor 16 is readily started and brought up to speed. In the first revolution of shaft 17, the paddle 21 is simply wound around the shaft until the torque required to turn the shaft and paddle is reduced to that developed by motor 16.
To provide the desired resilience in paddle 21 as Well as the necessary resistance to abrasion by the grit, said paddle is preferably constructed of a blade or sheet 25 of elastomeric or resilient material and a backing plate or sheet 26 of resilient metal such as spring steel. Blade 25 and its supporting backing plate 26 are secured to the lower end of shaft 17 by suitable screw fasteners 27, 28. The lower edge 29 of the blade 25 is made to conform generally with the contour of the bottom surface 30 of the container and is disposed either in light contact therewith, or with a slight separation therefrom to avoid undue wear of both the blade 25 and bottom Wall.
At the position of attachment of the agitator blade 21 to the shaft 17, the latter is notched to provide a surface 31, the plane of which is inclined to the axis of rotation of shaft 17. This inclination imparts a small vertical component of movement to the vehicle and grit to insure thorough agitation and uniformity in the composition of the lapping compound. The angular mounting also results in a raising of the bottom edge 29 from the surface 30 of the bottom wall 11 when the paddle 21 is bent, as shown in dotted lines in FIG. 6, which assists in withdrawing the blade 25 from its groove 22 and causes the blade to ride over the top of the settled grit. The resilience of the blade and its backing plate 26 causes the bottom edges of both to scrape over the top of the settled grit to erode it and put it back into suspension.
The blade 25 and its backing plate will tend to revert back to their normal fiat condition and as soon as the settled out grit at the bottom of container is in suspension, the outer regions of blade 25 will contact the radius 13 as well as the side wall 12 to insure a thorough agitation of all of the lower regions of the container. No gn't will be permitted to settle out in the corner at the radius 13.
The shapes of both the blade 25 and backing plate are preferably tapered from shaft 17 to the side Wall 12 to provide progressively greater yieldability of the blade as a whole. The radial dimension of backing plate 26 is dependent to a large extent upon the stiffness of blade 25, a relatively soft blade requiring support over a greater radial length than a relatively still one.
In operation, approximately the first one-half revolution of the shaft 17 pulls the paddle 21 sidewise in'groove 22 and tends to wrap the paddle around the said shaft. The paddle then bends upwardly and begins to scrape along-the top of the settled-out abrasive at the bottom of the container. As the abrasive is eroded, the paddle seeks its normal operating position wherein the top of the paddle rides over the side wall 12 and the compound is thoroughly agitated as required.
Although the agitator paddle has been described as applied'to a container for lapping compound, it is understood that the same paddle can be used with other containers and other substances normally held in suspension in a liquid vehicle, but which settle out when standing without agitation.
It is understood that the foregoing description is merely illustrative of a preferred embodiment of the invention and that the scope of the invention is not to be limited thereto but is to be determined by the appended claims.
1. In combination, a cylindrical container for liquids having substances normally held in suspension therein,
said container having bottom and side walls, an agitator shaft extending into the container and rotatable about an axis disposed substantially normally to the plane of the bottom wall, and an agitator paddle secured to the shaft, said paddle being comprised 'of 'a sheet of resilient metal secured at one end to the shaft and extending radially into proximity to the side walls and downwardly into close proximity to the bottom wall, and a' sheet of elastomeric material overlying the sheet metal and secured thereto, said elastomeric material extending radially into contact with the side walls and downwardly into light contact with the bottom wall, said elastomeric sheet being disposed in advance of the resilient metal sheet as the paddle moves through the liquid and substances in the container such that the resilient sheet metal forms a backing for the elastomeric material, the shaft having a substantially flat surface formed in the side thereof adjacent the bottom of the container, the plane of said fiat surface being angularly disposed with respect to the axis of the shaft, with the greatest distance between the shaft axis and flat surface occurring nearest the bottom of the container, and said paddle being secured to the shaft over said flat surface, whereby the edge of the paddle adjacent the bottom container wall is caused to rise above the said bottom wall as the paddle flexes due to resistance to movement thereof through the liquid.
2. In combination, a container for liquids having substances normally held in suspension therein, said container having a substantially flat bottom wall, an agitator shaft extending into the container and rotatable about an axis disposed substantially normally to the plane of the bottom wall and an agitator paddle secured to the shaft, said paddle being comprised of resilient sheet material extending substantially radially outwardly from the shaft and adapted to flex in response to tangential forces therein into a spiral form of reduced diameter whereby to reduce the resistance to rotation created by the paddle as it moves through the liquid in the container, the plane of the sheet material at the point of attachment to the shaft diverging from the axis of the shaft in the direction of the bottom of the container, such that as the sheet material flexw, it moves farther from the bottom of the container.
References Cited in the file of this patent UNITED STATES PATENTS 906,836 Volckening Dec. 15, 1908 912,085 Davis Feb. 9, 1909 1,430,070 Franzwa Sept. 26, 1922 2,493,049 Wernig Jan. 3, 1950 2,788,197 True Apr. 9, 1957 FOREIGN PATENTS 63,906 Germany Aug. 17, 1892 506,322 Canada Oct. 5, 1954 517,340 Great Britain Ian. 26, 1940