Abstract:
Apparatus is described for use in an industrial plant that contain machines (14) having oil reservoirs (12), which facilitates cleaning of the oil. The apparatus includes a stand (20) and equipment mounted on the stand, including input and output hoses (36,38) whose ends can be dropped into a machine oil reservoir. The equipment on the stand also includes a centrifuge (24), pump (26), valve (34), and porous filter device (40). In a first mode of operation, the pump draws oil from the reservoir to flow through the input hose into the centrifuge, and then to the output hose to flow back to the reservoir. The valve can be switched to a second mode wherein fluid from the input hose is directed through the pump to the porous filter device, for final cleaning of the oil before returning it to the reservoir. The stand has wheels to enable it to roll to another machine and clean its oil.

Description:
BACKGROUND OF THE INVENTION 
     Many industrial plants contain machines with hydraulic actuators, and with oil reservoirs where the hydraulic fluid, or oil, is stored. The oil becomes contaminated with dirt during use, and becomes contaminated with water especially due to condensation when the machine is not used at night and on weekends. One approach to cleaning the oil is to provide a dedicated cleaning system for the machine, such as a centrifugal pump which separates water and dirt from oil. U.S. Pat. No. 4,431,540 by Budzich shows a system of this type. However, this can add substantially to the space requirements and cost of the machine. An oil cleaning system for an industrial plant, which minimized the space requirements and cost for oil cleaning and which enabled very extensive cleaning when necessary, would be of considerable value. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the present invention, an apparatus and method are provided for the cleaning of the oil reservoirs of machines in an industrial plant, which minimizes the costs and enables cleaning to a range of oil purities. The system includes a stand and equipment thereon which includes a centrifuge, pump device, directional valve, input and output hoses, and porous filter device. The stand is placed adjacent to a machine oil reservoir and the hoses are dropped into the reservoir from its open top. The valve device is switched to a first state and the equipment operated to pump oil out of the reservoir and through the centrifuge where water and dirt is removed, with the clean oil delivered back to the reservoir. The centrifuge is operated continually until the amount of oil that has passed through the centrifuge for cleaning, is a plurality of times greater than the capacity of the oil reservoir, and preferably at least ten times as great. The valve is then operated in a second state, where oil is drawn out of the reservoir through the inlet hose and pumped to the porous filter device where the last bits of contaminants are removed, the very clean oil then being discharged back to the reservoir. The stand preferably has rollers, so that after processing oil in one machine reservoir, the apparatus can be rolled to another machine to process its oil. 
     The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of oil cleaning apparatus, shown in conjunction with the oil reservoir of a machine tool. 
     FIG. 2 is a diagrammatic view of the oil cleaning apparatus of FIG. 1, with the directional valve device in a first state. 
     FIG. 3 is a view similar to that of FIG. 2, but with the directional valve in a second state. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates an oil cleaning apparatus (10) which is shown used in conjunction with a tank or reservoir (12) of a machine tool (14). The machine tool, such as an injection molding press which has hydraulic actuators, includes a large oil reservoir (12) to enable hot oil to cool before it is reused in the actuators. The oil (16) becomes contaminated through dirt such as particles picked up from the actuators and the environment, and from water that condenses when the heated machine cools when the factory is unheated as at night or on weekends. The reservoir (12) normally has a cover over the top, which has been removed. 
     The oil cleaning apparatus (10) includes a stand (20) which lies on rollers (22) to enable the stand and equipment thereon to be readily moved around the industrial plant. Equipment mounted on the stand includes a centrifuge (24), a pump device (26) that includes first and second pumps (30), (32), a directional valve device (34) with two inlets and four outlets, input and output hoses (36), (38), and a porous filter device (40). An electrically energized motor (42) of the pump device, receives power through a cable, not shown, and is the only piece of equipment that is energized by an external power source. 
     To clean the oil in the reservoir (12) of the machine tool, applicant rolls the cleaning apparatus (10) to the vicinity of the reservoir and drops the outer ends (50), (52) of the input and output hoses into the reservoir. Preferably, the end (50) of the input hose lies near the bottom of the pool of oil of the reservoir near one end thereof, while the outer end (52) of the output hose lies near the top of the reservoir or pool near an opposite end thereof. The flexible hoses preferably each have a length of at least one meter, to easily reach into a reservoir. To start the cleaning operation, applicant operates the directional valve (34) to make the connections shown in FIG. 2. In FIG. 2, oil from the reservoir passes out through the input hose (36) and a conduit (60) to the first stage suction pump (30), and from the pump to a first inlet port (62) of the directional valve. With the valve in the first state shown, the pumped fluid from the reservoir flows out through a first valve outlet (64) and through a conduit (66) to an oil inlet (70) of the centrifuge. Fairly well cleaned oil, wherein most of the original contaminants including water has been removed, flows out of the centrifuge oil outlet (72) and through a conduit (74) to a second valve inlet (76). Water and dirt flow out of the centrifuge through another centrifuge outlet (78) to a holding tank (79). With the valve in its first state, oil from the centrifuge flows out of a second valve outlet (80) through a conduit (82) to the second stage pump (32) and flows from the second stage pump along the output hose (38) back to the reservoir (12). 
     The centrifuge may be of the type described in U.S. Pat. No. 4,431,540, which uses pressured oil pumped to a moderate pressure, such as up to 70 psi, by the first stage pump (30). Clean oil exiting from the centrifuge exits through jets which drive the centrifuge. Such centrifuges are available, which have an internal oil storage volume of about 0.5 gallons, and which have a through-put of about 3 gallons per minute. A common industrial hydraulic tool may have a reservoir of perhaps one hundred gallons to always provide cool oil. After about one half hour of operation of the centrifuge, about one hundred gallons of oil will have flowed through the centrifuge. 
     If applicant were to store all of the centrifuged oil before returning it to the machine tool reservoir, then after perhaps one half hour, all of the oil in the reservoir would have been moderately cleaned, and this oil could be dumped back into the reservoir. However, it is not usually practical to store the cleaned oil before returning it, because it is desirable to maintain a large level of oil in the reservoir during cleaning of the oil, to enable the machine tool to operate while the cleaning operation proceeds. Also, additional bulky equipment would be required to store the clean oil before dumping it back into the reservoir. Instead, applicant runs the centrifuge a plurality of times more than the above-mentioned period of thirty minutes, to clean an amount of oil which is a plurality of times the reservoir capacity. Preferably, applicant runs the centrifuge for at least 5 hours, so that at least ten times as much oil has passed through the centrifuge as the amount of oil (100 gallons) in the reservoir. Although the cleaned oil returned to the reservoir constantly mixes with some dirty oil left in the reservoir, the large flow of oil through the centrifuge, combined with placing the hose ends at different ends of the reservoir, results in a high proportion such as 95%, of the oil in the reservoir being as clean as the output of the centrifuge. The remaining perhaps 5% of initially unclean oil, causes only mild contamination of the clean oil. 
     FIG. 3 shows the equipment wherein the directional valve at 34A has been switched to its second state. In the second state, oil is drawn from the reservoir through the input hose (36) by the first stage pump (30). Oil flows from the pump into the first inlet port (62) of the valve and out through a third outlet port (90) of the valve and through a conduit (92) to the inlet (94) of the porous filter (40). The porous filter (40) is of the type used in automobiles and trucks and which is packed with porous filter material, except that the particular porous filter (40) is larger than most vehicle filters and the filter is constructed to remove water and to remove particulates greater than 0.5 microns. Very clean oil exits from the porous filter through its outlet (96), and flows through a conduit (98) to a manifold (100) that connects to the output hose (38) that delivers the clean oil back to the reservoir (12). The flow rate through the particular filter 40, used with the above-described centrifuge, is about 3.0 to 4.0 gallons per minute. 
     While the porous filter (40) produces extremely clean oil, the filter quickly becomes clogged if the oil flowing into the filter has a lot of contaminants such as dirt or water. The presence of the centrifuge (24) to remove most of the contaminants from the reservoir, prior to the relatively clean oil in the reservoir passing through the porous filter, results in a long life for the porous filter. A long life is desirable to minimize the considerable cost for the porous filter, and to save on the labor required in replacing the porous filter. 
     It may be noted that when the directional switch is in its second state shown at 34A, oil left in the centrifuge (24) at the moment of switching passes through the second valve inlet (76) and out through a fourth valve output port (102) to the manifold (100). At that time, a bleeder valve (104) on the centrifuge opens, to allow oil to drain out of the centrifuge, the oil being drawn out partially by being drawn into the flow of oil through the manifold (100). It also should be noted that a coupling (106) is located along the inlet conduit (60), so that some of the oil drawn from the reservoir passes through conduit (108) through the second stage pump (32) to flow to the manifold, without passing through the porous filter. The reason for pumping oil through the second stage pump (32), is to keep the pump (32) constantly lubricated with oil in a simple manner, to avoid wear. 
     Where the reservoir contains perhaps one hundred gallons of oil, a plurality of hundreds of gallons and preferably at least one thousand gallons, is pumped through the porous filter to provide very clean oil for the reservoir. The valve (34) shown in FIG. 1, can be manually operated, and also can be set to be operated by a control box (110) which has controls that keep the valve in its first stage for a predetermined period such as 5 hours, and then automatically switches the valve to the second stage and operates it for another period such as another 5 hours, and then shuts off the electric motor (42) which is the sole externally energized part of the apparatus. After oil in the reservoir (12) has been cleaned, and a worker notices that the machine has shut down after the appropriate period of time, a worker can then pull out the hoses from the reservoir and wipe oil off their ends. The worker then rolls the stand or frame with the equipment thereon to another machine tool, and drops the hose ends into the reservoir thereof to clean the oil of that reservoir. 
     In some localities a dam, indicated at 114, is required around oil processing apparatus. Applicant can establish a single dam (114), as by placing the dam on the stand or rolling the stand over an edge of the dam, using a relatively small dam, because all the processing equipment is mounted on a single stand. 
     Thus, the invention provides apparatus for cleaning oil, and especially for separating water from the oil, which can be readily used in an industrial plant. This is accomplished by mounting various equipment on a single stand, with flexible hoses that can be dropped into a reservoir of a machine tool. The equipment preferably includes a directional valve, a centrifuge, a pump device with at least one pump, input and output hoses, and a porous filter device. In one state of the valve, oil from the reservoir is passed through the centrifuge for relatively good cleaning. The amount of oil passed through the reservoir is preferably a plurality of times greater than the pool of oil in the reservoir and preferably at least ten times as great, to effectively clean the oil without having to separately store all of the reservoir oil before dumping it back into the reservoir. The valve can be set in either of two stages, so that after centrifuging the oil, the oil can be repeatedly passed through the porous filter for fine cleaning. 
     Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.