Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed toward metal casting processes and, more particularly, toward a method and device for recovering and recycling die lubrication used in such metal casting processes. 
     2. Description of Related Art 
     In metal casting applications, it is common practice to spray lubricating agents on the dies to cool the dies and to assist in releasing the cast part from the dies. The lubricating or release agents are diluted with water to varying degrees depending upon the part being made and the specific problem being addressed. For example, a normal ratio of water to lubricant may be about 70:1, and a ratio of water to release agent of 25:1 may be used in situations wherein the molded material sticks to the die, etc. Different ratios may also be used on the same die, wherein more lubrication is applied to problematic areas, typically to locations experiencing heat build up due to the configuration of the die. Moreover, individual dies may have multiple sprays sequentially applied thereto at different times during the casting process. 
     With reference to FIG. 4, a conventional die lubrication system  10  is illustrated to include a pressure intensifier  12 , a die lube source  14 , a die spray device  16 , and a used die lube collection pan  18 . The die lube source  14  is fluidly connected, via a pipe  20 , a manually operated shut-off valve  21 , and an inlet check valve  22 , to the pressurizing cylinder  24  of the pressure intensifier  12 . Controlled application of a hydraulic source  26  to the master piston  28  of the pressure intensifier moves the piston up and down to selectively draw die lube past the inlet check valve  22  and into the pressure intensifier pressurizing cylinder  24  and then expel pressurized die lube from the pressure intensifier pressurizing cylinder. Pressurized die lube flows through an outlet pipe  30  and outlet check valve  32  to the die spray device  16 . The used die lube is collected in the collection pan  18  and directed to the drain  34  and, ultimately, to the plant wastewater treatment facility. 
     Unfortunately, this common practice is wasteful of die lube, which is relatively expensive and may be used many times if separated from contaminants. Moreover, the processing of waste die lube is a major source of the manufacturing facility waste treatment load. Therefore, there exists a need in the art for a method and device for cleaning and reusing die lube. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward a method and device for cleaning and reusing die lube. 
     In accordance with the present invention, a die lube recovery system includes a weir tank, an oil skimmer, a recovery pump, a filtration assembly, and a holding tank. The weir tank receives used die lube and includes means to filter large particles from the used die lube. The oil skimmer is associated with the weir tank and is operable to remove oil from the used die lubrication. 
     In further accordance with the present invention, the filtration assembly removes particulates from the used die lube output from the weir tank and supplies reconditioned die lube to the holding tank. The recovery pump forces fluid from an outlet of the weir tank to an input of the filtration assembly. 
     In further accordance with the present invention, the holding tank contains a quantity of reconditioned die lube and has a first sensor for monitoring a liquid level in the holding tank. When a sensed level of reconditioned die lube in the holding tank falls below a first predetermined level, fresh die lube is added to the holding tank. 
     The system according to the present invention farther includes a fresh die lube source, a die lube pressure booster, and a die spraying device. The die lube source is fluidly connected, via a pipe and an automatically-operated valve, to the holding tank such that, when the sensed level of reconditioned die lube falls below the predetermined level, the automatically-operated valve is opened to permit fresh die lube to flow into the holding tank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and further features of the present invention will be apparent with reference to the following description and drawings, wherein: 
     FIG. 1 schematically illustrates a die lube reclamation system according to the present invention; 
     FIG. 2 is a perspective view of a weir tank according to the present invention; 
     FIG. 3 is a perspective view of a holding tank according to the present invention; and, 
     FIG. 4 schematically illustrates a conventional die lube system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     It should be noted that in the following detailed description, identical components have the same reference numerals, regardless of whether they are shown in different embodiments of the present invention. It should also be noted that in order to clearly and concisely disclose the present invention, the drawings may not necessarily be to scale and certain features of the invention may be shown in somewhat schematic form. 
     With reference to FIG. 1, a die lube recovery system  100  is schematically illustrated. The system  100  includes a weir tank  102 , a filtration assembly  104 , a holding tank  106 , and a source of fresh die lube  14 . The system further includes a hydraulic pump that serves as a die lube pressure booster  12  to supply pressurized die lube to the dies via the spray device  16 , as will be clear from the following description. 
     A collection pan  18  directs used die lube, via a collection trough  110 , to the weir tank  102  for gross filtration and oil removal. As shown best in FIG. 2, the weir tank  102  has three compartments: a first compartment  102   a  for gross filtration and oil skimming, a second or middle compartment  102   b  to limit transmission of floating and submerged particles, such as flashing, and a compartment  102   c  from which preliminarily cleaned die lube is output. 
     The first compartment  102   a  of the weir tank  102  has an inlet  112  at a top thereof through which flows dirty lube from the machine collection trough  110 . Opposite the inlet  112  is an overflow connection  114  through which through which excess fluid can flow to drain, if necessary. A drain coupling  116  is also provided at a bottom of the first compartment  102   a  which, by means of a manually operated valve  118  (FIG.  1 ), permits the first compartment  102   a  to be drained of fluid for maintenance purposes. A basket-type mesh filter  120  (FIG. 1) is removably received in the first compartment  102   a  and is operable to remove larger particles entrained in the dirty stream of die lube entering the weir tank  102 . The basket filter  120  is easily removed from the weir tank  102  and emptied, as will be desirable periodically. An oil skimmer  122  is preferably mounted at the first compartment  102   a  and is operable to remove waste oil from the fluid therein. The removed waste oil is delivered to a waste oil container  124  for recycling. 
     A first wall  126  separates the first and second compartments  102   a ,  102   b  and serves to contain floating debris within the first compartment  102   a . An upper edge  126   a  of the first wall  126  is at least as high as the overflow connection  114 , while a lower edge  126   b  of the wall  126  is spaced from a bottom wall  103  of the weir tank  102 . Therefore, lube flows under the first wall  126  and into the second compartment  102   b.    
     A second wall  128  separates the second compartment  102   b  from the third compartment  102   c . A lower edge  128   b  of the second wall  128  is sealed to the bottom wall  103  of the weir tank  102  to prevent submerged debris from entering the third compartment  102   c . An upper edge  102   a  of the second wall  128  has a notched-out portion  128   c  to permit an upper portion of the lube within the second compartment  102   b  to flow into the third compartment  102   c.    
     The third compartment  102   c  has a drain coupling  130  at a bottom thereof. The third compartment  102   c  can be emptied of fluid by opening a manually operated valve  132  (FIG. 1) disposed in the line connected to the drain coupling  130 . First and second outlet couplings  134 ,  136  are provided in the sidewall opposite the drain outlet  130  in the third compartment  102   c . The first coupling  134  is relatively closer to the bottom wall  103  of the weir tank  102  and is connected, via a pipe  138  and a strainer  139 , to a return pump  140  that supplies preliminarily filtered die lube to the filtration assembly  104 . The second coupling  136  is used as a fluid connection for a float switch  142  (FIG. 1) that senses the lube level in the third compartment  102   c  and activates/deactivates the pump  140  accordingly. 
     As shown in FIG. 1, the pump  140  is provided downstream the weir tank  102  and is controlled, by means of the aforementioned float switch  142 , to pump preliminarily filtered die lube to a pair of parallel-connected filter  104   a ,  104   b  of the filtration assembly  104 . The return pump  140  is preferably a commercially available diaphragm-type air pump and pressurizes the preliminarily filtered die lube so as to force the lube through the filters  104   a ,  104   b . The filters further clean the preliminarily filtered lube, and preferably are adapted to farther remove particulate matter, preferably including oil, from the fluids flowing therethrough. Suitable fluid connections and valving, as illustrated, is provided such that either of the filters  104   a ,  104   b  may be taken off-line for maintenance, cleaning and/or replacement of filter media. Each of the filters  104   a ,  104   b  includes a drain pipe, normally closed by a manually operated ball valve, to communicate fluid to the available trench drain, as will be desirable during back flushing or maintenance. 
     The further filtered lube (hereinafter referred to as reconditioned die lube) flows from the filtration assembly  104 , through a pipe  143 , and into the holding tank  106 . In addition to receiving reconditioned die lube, the holding tank  106  is available to receive fresh die lube from the fresh die lube source  14 . Reconditioned die lube from the holding tank is delivered to the die lube booster cylinder  12 , which is operable to supply pressurized die lube to the die spray heads  16 , as will be described hereinafter. 
     With reference to FIG. 3, the holding tank  106  defines a container having a series of upstanding sidewalls  106   a ,  106   b ,  106   c ,  106   d  and a bottom wall  106   e  . The bottom wall  106   e  has a drain fitting  107  therein to permit the holding tank  106  to be drained of fluid. A first sidewall  106   a  has an overflow coupling  144  at a top portion thereof that serves to direct excess fluid to drain. A second sidewall  106   b  has a coupling  146  at a top portion thereof that receives the pipe  143  extending from an output of the filtration assembly  104 . 
     A third sidewall  106   c  has a coupling  148  at a top portion thereof that receives a holding tank fill pipe  158  extending from the fresh die lube source  14 , to be described further hereinafter. The third sidewall  106   c  also has a larger coupling  152  at a bottom portion thereof through which reconditioned die lube flows toward the pressure intensifier  12  via a holding tank outlet pipe  154 . 
     A fourth sidewall  106   d  has first and second switch couplings  156 ,  158 . The first switch coupling  156  is disposed close to the top edge of the fourth sidewall  106   d  and is in fluid communication with a float switch  160  (FIG. 1) that activates/deactivates a solenoid valve  162 . The solenoid valve  162  is operable to control introduction of fresh die lube (via the coupling  148 ) into the holding tank  106 . The second switch coupling  158  is disposed relatively beneath the first switch coupling  156  and is in fluid communication with a float switch  164  (FIG. 1) that senses low fluid level in the holding tank  102  to initiate a cycle stop when the fluid level falls below the level of the second switch coupling  158 . Each of the float switches  142 ,  160 ,  164  employed in the present invention preferably has a time delay associated with the switching function to prevent transient level fluctuations, as may be caused by turbulence in the tanks  102 ,  106 , from negatively affecting operation of the system  100 . 
     With reference to FIG. 1, the die lube source  14  is fluidly connected, via a pipe  20 , a first manually operated valve  21 , and an inlet check valve  22 , to the pressurizing cylinder  24  of the pressure intensifier  12 . Between the die lube source  14  and the first manually operated valve  21 , the pipe  20  is T-connected to a holding tank fill pipe  150  extending toward the holding tank  106  and connected to the connector  148 . The holding tank fill pipe  150  has a second manually operated valve  166  and the solenoid valve  162  disposed therein. The solenoid valve  162  is opened/closed by the float switch  160  of the holding tank  106  to automatically control the introduction of fresh die lube into the holding tank  106 . More specifically, when the reconditioned lube level in the holding tank  106  is lower than a first predetermined level, the float switch  160  closes to actuate or open the solenoid valve  162 . When the reconditioned die lube level is greater than a second predetermined level, the float switch  160  opens, de-actuating and thereby closing the solenoid valve  162  and preventing further introduction of fresh die lube from the die lube source  14  into the holding tank  106 . 
     The holding tank outlet pipe  154  is T-connected to the source pipe  20  relatively between the first manually operated valve  21  and the check valve  22 , as illustrated. A third manually operated valve  170  is provided in the outlet pipe  154  near an outlet of the holding tank  106 . The check valve  22  permits fluid flow only in a direction relatively toward the pressure intensifier  12 , thereby preventing back-flow of reconditioned lube. As will be appreciated by those skilled in the art, the first manually operated valve  21  is normally closed, and the second and third manually operated valves  166 ,  170  are normally opened during operation of the die lube reclamation system  100 . However, the first manually operated valve  21  can be opened, and the second and third valves  166 ,  170  closed, to take the die lube reclamation system  100  off-line, as may be necessary for significant repairs, such as should the pump fail. Closing the second and third valves  166 ,  170  will isolate the holding tank  106  from the die lube source  14 . 
     Controlled application of a hydraulic source  26  to the piston  28  of the pressure intensifier  12  moves the piston up and down to selectively draw die lube into the pressure intensifier pressurizing cylinder  24  from the holding tank  106  and then expel pressurized die lube from the pressure intensifier pressurizing cylinder  24 . Pressurized die lube flows through the outlet pipe  30  and outlet check valve  32 , to the die spray device  16 . The used die lube is collected by the die lube collection pan  18  and the recycling process continues again. 
     The present invention has been described herein with particularity, but it is noted that the scope of the invention is not limited thereto. Rather, the present invention is considered to be possible of numerous modifications, alterations, and combinations of parts and, therefore, is only defined by the claims appended hereto.

Technology Category: b