Method of mixing viscous fluids

A method of mixing viscous fluids is disclosed. The method comprises rotating a mixing apparatus (20) in a container (42) of fluid (44). The mixing apparatus comprises a cage (21) located at the end of the shaft (22). The cage (21) comprises a central circular disc (24) with an outer edge (43) and top (38) and bottom (40) sides. A number of vanes (26) extending from each side of the disc (24), the vanes (26) spacedly located near the outer edge of the plate. The free ends of the vanes (26) are connected by a hoop (38,40) to maintain their spaced relationship.

FIELD OF THE INVENTION

The present invention relates to a method of mixing fluids. More particularly, the present invention is a method of mixing viscous fluids by rotating a multi-vaned mixer.

BACKGROUND OF THE INVENTION

The mixing of viscous fluids has historically been a difficult task. Present methods of mixing such fluids often result in inadequate mixing and are time-consuming and energy consumptive.

One of the more common viscous fluids which must be mixed is paint. Homeowners and painters are all too familiar with the task of mixing paint.

Probably the most common method of mixing fluid such as paint involves the user opening the container, inserting a stir stick or rod and rotating or moving the stick about the container. This method is tiring, requiring tremendous effort to move the stir stick through the viscous fluid. Because of this, individuals often give up and stop mixing long before the paint is adequately mixed. Further, even if the individual moves the stir stick for a long period of time, there is no guarantee that the paint is thoroughly mixed, rather than simply moved about the container.

Many mechanisms have been proposed for mixing these fluids and reducing the manual labor associated with the same. These mechanisms have all suffered from at least one of several drawbacks: users have difficulty in using the device because of its complexity or size, the device inadequately mixes the fluid, the device mixes too slowly, the device does not break up or “disperse” clumped semi-solids in the fluid, and/or the user has a difficult time cleaning up the device after using it. Other problems associated with these mixers are that they often introduce air into the fluid (which, in the case of paint is detrimental, for example, when the paint is to be sprayed with a sprayer), and some of the mixing devices may damage the container in which the fluid is being mixed, causing the fluid to leak from the container.

One example of such a mechanized mixing device is essentially a “screw” or auger type device. An example of such a device is illustrated in U.S. Pat. No. 4,538,922 to Johnson. This device is not particularly effective in mixing such fluids, as it imparts little velocity to the fluid. Further, the device does not disperse clumped fluid material, but simply pushes it around the container.

Another method for mixing paint comprises shaking the paint in a closed container. This can be done by hand, or by expensive motor-driven shakers. In either instance, the mixing is time consuming and often not complete. Because the shaking occurs with the container closed, little air space is available within the container for the fluid therein to move about. Therefore, the shaking often tends to move the fluid very little within the container.

Several devices have been developed for mixing paint which comprise devices for connection to drills. For example, U.S. Pat. No. 4,893,941 to Wayte discloses a mixing device which comprises a circular disc having vanes connected thereto. The apparatus is rotated by connecting a drill to a shaft which is connected to the disc. This device suffers from drawbacks. First, the limited number of vanes does not provide for thorough mixing. Second, because the bottom disc is solid, no fluid is drawn through the device from the bottom. It is often critical that fluid from the bottom of the container be drawn upwardly when mixing viscous fluids, since this is where the heaviest of the fluids separate prior to mixing.

U.S. Pat. No. 3,733,645 to Seiler discloses a paint mixing and roller mounting apparatus comprising a star-shaped attachment. This apparatus is not effective in mixing paint, as it does not draw the fluid from the top and bottom of the container. Instead, the paddle-like construction of the device simply causes the fluid to be circulated around the device.

U.S. Pat. No. 1,765,386 to Wait discloses yet another device for mixing liquids. This device is wholly unacceptable, as it must be used in conjunction with a diverter plate located in the container to achieve adequate mixing. Use of the diverter plate would either require its installation into a paint container before being filled, which would increase the cost of paint to the consumer, or require that the consumer somehow install the device into a full paint container.

An inexpensive method for mixing viscous fluids in a quick and effective manner is needed.

SUMMARY OF THE INVENTION

The present invention is a method of mixing viscous fluids. The method comprises locating a mixing device in a container of fluid and rotating said device in said fluid with rotary drive means. The mixing device preferably comprises a mixing cage connected to the shaft.

The shaft is elongate, having a first end connected to a central plate and a second free end for connection to the rotary drive means. The plate is solid, circular, and has a top side, bottom side, and outer edge.

Vanes in the form of thin, curved slats, are spacedly positioned about the outer edge of each side of the plate. The vanes extend outwardly from each side of the plate parallel to the shaft. A first end of each vane is connected to the plate near the outer edge thereof. The vanes are connected at their second ends by a hoop.

The vanes preferably have a length which is between about 0.1-2 times the diameter of the plate. The number of vanes located about each side of the plate preferably number between 4 and 12 per inch diameter of the plate. Each vane preferably extends inwardly from the periphery of the plate no more than about 0.1-0.35 of the distance from the center of the plate to the periphery thereof at that location.

In use, a user positions the mixing cage of the device in a container of fluid. The user connects the free end of the shaft to the rotary drive means, such as a drill, and rotates the cage within the fluid.

The device has been found to be extremely effective in mixing viscous fluids such as paint. The device draws fluid, without the need of a diverter plate, from the top and bottom of the container. The fluid is dispersed at high velocity radially outwardly through vanes.

The device is easy to use, and a user need only connect it to a drill. The device is easy to clean, the user needing only to relocate it and rotate it in a container of cleaning fluid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention comprises a method of thoroughly mixing a fluid with a mixing device. In general, the method comprises rotating the mixing device in a container containing fluid. As used herein, the term “fluid” is intended to mean liquids, especially those of viscous nature whether containing dissolved or undissolved solids, slurries, gels or those groupings of solid or semi-solid materials which behave in some respects as a fluid, such as granular materials (e.g. flour, sugar, sand, etc.).

As illustrated inFIG. 1, the mixing device20generally comprises a cage-like structure having open ends. As illustrated inFIG. 5, the device20includes a shaft22for rotation by rotary drive means such as a drill46, the shaft connected to a central plate connecting plate24. Vanes26extend outwardly from each side of the central connecting plate24parallel to the shaft22. The vanes26are connected at their ends opposite the plate by a hoop28,30.

In use, a user positions the mixing device in a container42of fluid44. The user connects the shaft22of the device20to a drill46and rotates it within the fluid. As illustrated inFIG. 5, the mixing device20mixes the fluid by drawing it from the top and bottom of the container42and forcing it radially outward through the vanes26.

The mixing device20for use in the present invention will now be described with more particularity with reference toFIGS. 1-5. In general, and as illustrated inFIG. 1, the device20includes mixing cage21connected to a shaft22, the mixing cage21comprising a central connecting plate24, vanes26, and two hoops28,30.

The shaft22is an elongate rigid member having a first end32and second end34. The exact length and diameter of the shaft22depends on the depth of the fluid in the container to be mixed. When the device20is for use in mixing paint in a standard one-gallon paint can, the shaft22can be about 8-9 inches long and about 0.25 inches in diameter.

The first end32of the shaft22is adapted for connection to a rotary drive means. Preferably, the rotary drive means comprises a drill, as illustrated in FIG.5. Preferably, the shaft diameter is chosen so that engagement with the rotary drive means is facilitated.

The second end34of the shaft22is connected to said central plate24. Preferably, the second end34of the shaft22engages an adapter36connected to the plate24. The shaft end34engages the plate24at the center point of the plate24.

The central plate24comprises a flat, disc-shaped member having a top surface38, bottom surface40and outer edge43. The shaft22engages the plate24at the top surface38thereof.

Preferably, the plate24is constructed of durable and fairly rigid material. The plate24may be any of a variety of sizes and shapes. When used for batch mixing of quantities of one gallon of highly viscous (i.e. resists flow) liquids such as paint, it is preferably 1-4, and most preferably about 2.5 inches in diameter.

A number of vanes26extend from the top and bottom surface38,40respectively, of the plate24or support near the outer edge43or periphery thereof. Each vane26has a first or inner edge and second or outer edge, being curved therebetween. As best illustrated inFIGS. 1 and 3, in one embodiment, although the vanes26are curved, the inner and outer edges thereof are generally aligned in a radial direction from the shaft22or an axis alone which the shaft extends. The curved shape of the vane26causes the vane to have a concave surface27and a convex surface29(see FIGS.2and4). All of the vanes26are oriented on the plate24in the same direction. The vanes26are oriented on the plate24in a manner such that they face in the direction of rotation indicated by arrow47in FIGS.1,2,4and5, when rotated by the rotational drive means46. In the embodiment illustrated inFIGS. 1,2and4, the first or inner edge of the vanes26generally faces the shaft22or axis along which the shaft22extends. Alternatively stated, as illustrated, the first or inner edge of each vane26defines a leading surface which is oriented generally perpendicular to a radial direction from the shaft22or the axis along which the shaft extends. Further, in an embodiment wherein the vanes22are curved, as best illustrated inFIGS. 1 and 3, adjacent vanes26define openings therebetween which are also generally curved. As illustrated, in one embodiment, at least a portion of one or more of these curved openings are generally radially aligned with the shaft22or the axis alone which the shaft extends.

The vanes26are preferably constructed of durable and fairly rigid material. It has been found preferable that the ratio of the length of the vanes26to the diameter of the plate be between about 0.1 and 2, and most preferably between 0.2 and 0.7. Moreover, it has been found preferable that the number of vanes26be dependent on the ratio of the diameter of the plate24on the order of about 4-12, and most preferably about 9 vanes per inch diameter of the plate24. The width of each vane26, is preferably no more than 0.1 to 0.35 times the radius of the plate24, and more preferably about 0.1-0.3, and most preferably about 0.25 times the radius of the plate24. The thickness of each vane26depends on the material from which it is made. Regardless of its width, each vane26is preferably positioned at the outer edge43of the plate24such that the vane26extends inwardly therefrom no more than about 0.1-0.35, more preferably less than about 0.3, and most preferably less than about 0.25, of the distance from the center of the plate24to the periphery thereof at that vane26location (i.e. less than about 0.35 the radius when the plate24is circular).

When the device20is configured for use in mixing paint in a one-gallon container and the plate24diameter is about 2.5 inches, the vanes26are preferably about 1 inch long from their ends at the connection to the plate24to their ends connected at the hoops28,30. Each vane26is preferably about 0.2-1, and most preferably about 0.3 inches wide.

In order to disperse partially solidified particulate in the fluid, the vanes26are fairly closely spaced about the outer edge43of the plate24. The vanes26are preferably spaced about 0.1-1 inch, and most preferably about 0.25 inches apart. When the vanes27are spaced far apart (e.g. about 1 inch) the vane width and/or height is preferably increased within the above-stated range or ratios. Thus, in the case where the plate24has a diameter of about 2.5 inches, there are preferably about twenty-four vanes26, as illustrated inFIGS. 1,2and4.

In order to prevent relative movement between the free ends of the vane26, this end of each vane is connected to a support hoop28,30. The hoop28,30comprises a relatively rigid circular member of “L” shaped cross-section. A first portion of each hoop28,30extends over the end of each of the vanes, and a second portion of each hoop28,30extends downwardly along the outer surface of each vane, as illustrated inFIGS. 2-4. In other embodiments, the hoops28,30may be configured and connected in other manners. Each vane26is securely connected to its corresponding hoop28,30.

Use of the device20described above in the method of the present invention will now be described with reference to FIG.5.

A user obtains a container42containing fluid44to be mixed. This container42may comprise a paint can or any other container. The fluid44to be mixed may comprise nearly any type of fluid, but the method of the present invention is particularly useful in mixing viscous fluids.

The user attaches the device20of the present invention to rotary drive means. As illustrated inFIG. 5, the preferred means comprises a drill46. The means may comprise apparatus other than a drill, however, such as pulley or gas motor driven means. These drive means preferably turn the shaft22of the device at speed dependent upon the viscosity of the fluid. For example, for low viscosity fluids, the rotational speed may be often as low as about 500 rpm, while for high viscosity fluids the rotational speed may often be as high as 1,500 rpm or more. The user attaches the first end32of the shaft22to the drill46, such as by locating the end32of the shaft in the chuck of the drill.

Once connected, the user lowers the mixing cage21into the fluid44in the container42. The user locates the mixing cage21below the top surface of the fluid.

Once inserted into the fluid44, the drill46is turned on, thus effectuating rotational movement of the mixing cage21. While the cage21is turning, the user may raise and lower it with respect to the top surface of the fluid and the bottom of the container, as well as move it from the center to about the outer edges of the container, so as to accelerate the mixing of the fluid therein.

Advantageously, and as illustrated inFIG. 5, the device20of the present invention efficiently moves and mixes all of the fluid44in the container42. In particular, because of the location of vanes extending from and separated by the central plate24, the mixing cage21has the effect of drawing fluid downwardly from above the location of the cage21, and upwardly from below the cage, and then discharging the fluid radially outwardly (as illustrated by the arrows in FIG.5). This mixing effect is accomplished without the need for a diverter plate in the bottom of the container.

As indicated above, the fluid may or may not contain dissolved or undissolved solids. Most importantly, if partially solid material or particulate is present in the fluid, that material/particulate is effectively strained or dispersed by the vanes26of the cage21. The close spacing of the vanes26traps unacceptably large undeformable globules of fluid or other solid or partially solid material in the cage, for removal from the cage after mixing. Other globules of partially solidified fluid material are sheared apart and dispersed when they hit the vanes, reducing their size and integrating them with the remaining fluid.

Advantageously, optimum mixing is achieved with the present device20as a result of the positioning of substantially long inner and outer vane edges at the periphery of the plate24. This allows the fluid moving though the device20to impact upon the inner edge of the vane26at a high radial velocity and therefore with great force. Further, the outer edge of the vane has a high velocity in relation to the fluid in the container positioned outside of the device20, thereby impacting upon that fluid with great force.

The ratio of the length of each vane to its width, and their placement at the periphery of the plate, creates maximum fluid flow through the cage21. This is important, for it reduces the total time necessary to thoroughly mix the fluid in a particular session.

Notably, the hoops,28,30protect the container from damage by the spinning vanes26. This allows the user to be less careful in positioning the cage21in the container42, as even if the cage21encounters the sides or bottom of the container, the cage is unlikely to damage the container.

Another advantage of the mixing device20of the present invention is that it mixes the fluid without introducing air into the fluid, as is a common problem associated with other mixers utilized for the same purpose. As can be understood, the introduction of air into a fluid such as paint is extremely detrimental. For example, air within paint will prevent proper operation of many types of paint sprayers and makes uniform coverage when painting difficult. The presence of air is also detrimental, for example, where a polyurethane coating is being applied, as air bubbles become trapped in the coating and ruin its appearance.

After the fluid has been adequately mixed, cleaning of the device20is fast and easy. A user prepares a container filled with a cleaning agent. For example, in the case of latex paints, water is an effective cleaning agent. The user lowers the cage21into the cleaning agent, and turns on the drill46. The rapid movement of the cleaning agent through the cage21causes any remaining original fluid (such as paint) or trapped globules thereon to be cleansed from the device20.

Once the device20is clean, which normally only takes seconds, the device can be left to air dry.

The dimensions of the device20described above are preferred when the device is used to mix fluid in a container designed to hold approximately 1 gallon of fluid. When the device20is used to mix smaller or larger quantities of fluid of similar viscosity, the device20is preferably dimensionally smaller or larger.

While the vanes26of the device20are preferably curved, it is possible to use vanes which are flat. The vanes26are preferably curved for at least one reason, in that such allows the vanes26to have an increased surface area without extending inwardly from the periphery towards the center of the plate24beyond the preferred ratio set forth above. Also, it is noted that while the vanes26extending from the top and bottom of the plate24are preferably oriented in the same direction, they may be oriented in opposite directions (i.e. the convex surfaces of the top and bottom sets of vanes26may face opposite directions).

In an alternate version of the invention, vanes only extend from one side of the plate. The vanes may extend from either the top or the bottom side. Such an arrangement is useful when mixing in shallow containers, while retaining the advantages of high fluid flow mixing rates and the straining capability. In this arrangement, or that where the vanes26do not extend from each side the same distance, it will be appreciated that the central plate24is not “central,” but still provides the supporting functions described.

It will be understood that the above described arrangements of apparatus and the method therefrom are merely illustrative of applications of the principles of this invention and many other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the claims.