Liquid purification or separation – Structural installation – Closed circulating system
Reexamination Certificate
1999-12-23
2002-03-19
Lithgow, Thomas M. (Department: 1724)
Liquid purification or separation
Structural installation
Closed circulating system
C210S122000, C210S194000, C210S242300, C210S416500, C210S923000
Reexamination Certificate
active
06358409
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to oil-water separation, and more particularly, to a small, compact apparatus designed to skim a layer of oil from an aqueous surface, usually a thin film resting on top of the water in an immersion tank, such as a hot tank or the like.
When skimming a thin film of oil or grease from the top surface of the water in an aqueous parts cleaner system, there are a number of problems commonly encountered. First, the skimmer must be designed so as to float on top of the water, but more importantly, to float at almost exactly a desired level. This is to insure that, under most conditions, only a very thin layer of water, and the oil resting on top thereof, be skimmed off. While the action of floating itself is not ordinarily a problem, especially with hot tanks and the like, the temperature of the water in immersion cleaners can vary considerably. It is not uncommon to find a variety of operating water temperatures of from 100° to 110° up to 180° or more. Even those baths that are intended to be carefully controlled have water temperatures that may fluctuate between 130° and 165° F., for example.
Consequently, assuming that a device has a body and an inlet that is intended to operate at exactly a certain level of submergence to skim the oil from the surface of the water, in other words, to have an exactly intended “skim gap”, thermal expansion of the floating body must be taken into account. If, for example, the skim gap is set at a certain dimension, say {fraction (7/64)}″, an increased water temperature will result in lower water density. This causes the floating body of a fixed volume and weight to sink down a slight amount, thereby increasing a preset skim gap.
Assuming there is a thin layer of oil on the water surface, enlarging the skim gap in turn would result in drawing an excess of water relative to oil into the collection tube. On the other hand, a reduction in temperature of the aqueous bath would cause the density of the aqueous bath to rise. This would cause the float to rise to a level whereby, in an extreme case, the skim gap would be entirely eliminated. Consequently, it would be desirable to have a floating skimmer which would be relatively insensitive to changes in temperature, at least throughout a significant range of the temperatures likely to be encountered in use.
Operating the aqueous bath in a narrow range of temperature, however, is not as easy as it may appear. This is because, in the case of some parts which are both massive and relatively cold, placing them into a heated immersion tank would lower the temperature considerably. The thermostat, although attempting to control the temperature, is still faced with a rather substantial induced variation in temperatures, at least in the short run. Furthermore, the materials from which the present skimmer is made obviate any problems with operating a hot tank at temperatures up to 180° F., for example.
The configuration of certain embodiments of the present invention is also important. This configuration is such that there is provided a horizontal inlet into the body within a recess formed by contoured side walls and, preferably a flat bottom shelf. The oil to be separated by the surfactant forms a relatively thin film on top of the water, in most cases. In some cases, of course, the oil film may be very thick at the beginning of a new cycle, however, within a short time it again assumes the dimensions of a thin film.
It is thought that when a thin layer of oil atop a layer of water passes through a skimmer's horizontal inlet, the water may cling to the lower shelf and establish a Prandtl boundary layer whose velocity gradient effects a certain amount of separation by retarding the flow of water relative to the oil layer.
Other considerations include the skim gap whose optimum value will vary depending, among other things, upon the type of pump used to remove the skimate. For example, a {fraction (7/16)}″ skim gap was found to work well with a bellows pump pumping at one pint per minute.
The skim gap is relatively critical and the float and weight construction of the present invention makes it easy to maintain such a relationship. Consequently, with a properly designed skimmer, substantial amounts of oil pass into the collection tube, and these can be readily removed therefrom by a pump.
In addition, it has been found that the body of the skimmer preferably should be located in a corner of the hot tank, inasmuch as, in most cases, convection currents caused by the heater generally favor flow of the oil film into a corner of the bath. Consequently, the skimmer is preferably oriented so that the opening in the skimmer faces outwardly from this corner area. The skimmer maintains this orientation by one or more novel and stable guide arrangements, yet none of which causes substantial friction by reason of moving up and down as the level of water changes in the tanks.
In view of the failure of the prior art to provide a small or compact, low cost, reliable skimmer that will skim a variety of oil films from the surface of a controlled environment, such as for example a hot tank, it is an object of the invention to provide an improved oil skimmer.
Another object of the present invention is to provide a skimmer which includes a submersible collection tube, and a contoured inlet to such tube formed in the side wall of a floating body.
Yet another object of the present invention is to provide a floating body which includes one or several floats in addition to the principal body member itself.
Still another object of the present invention is to provide a skimmer which includes at least one guide, and in some cases two guides, extending down through one of the floats (and elsewhere) to guide the skimmer in its vertical movement.
A further object of the present invention is to provide a floating skimmer which includes plural floats and a body as well as an inlet formed in the body, and whose vertical movement is determined by two guides which permit only vertical movement of the skimmer.
A still further object of the present invention is to provide a relatively fixed suction tube for oil and water which are made to accumulate in a collection tube.
An additional object of the present invention is to provide, in a different embodiment, a shallow collection cup and an extensible suction hose or the like for continuously withdrawing oil and water from the collection cup.
Another object of the present invention is to provide a collection tube which in one embodiment, is concentrically arranged with a suction tube, serving the dual function of acting as a guide for movement of the skimmer as well as collecting the mixture that accumulates therein.
Still another object of the present invention is to provide a skimmer and an appropriate fluid circuit for removing an oil-aqueous solution from the surface to be skimmed, depositing the mixture in a reservoir and returning the aqueous solution from the bottom of the reservoir to the hot tank, allowing the oil eventually to accumulate to a point where it substantially fills the reservoir.
Yet another object of the present invention is to provide a skimmer which is operable with a low-capacity intermittent suction pump.
Still another object of the present invention is to provide a skimmer with a horizontal opening for oil-aqueous solution, with the opening surrounded being by a flat shelf portion defined by contoured side walls.
A further object of the present invention is to provide a tank for aqueous solution and an oil film with a skimmer device which resides in one corner of the tank, preferably having the skimmer shrouded where it is protected from contact with parts which are immersed in the tank.
A still further object of the present invention is to provide a skimmer which is small, reliable and which may be produced at relatively low cost.
Another object of the present invention is to provide a skimmer having a readily accessible provision for adding or taking off weight in small increments to vary the skim
Anderson Harold Donald
Danowski Thomas J.
Jacoby, Jr. William L.
Lithgow Thomas M.
Safety-Kleen Systems, Inc.
Vedder Price Kaufman & Kammholz
LandOfFree
Oil skimmer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Oil skimmer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oil skimmer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2875746