The present invention relates to fluid jet systems for cutting, polishing and other machining operations, and more particularly to closed loop fluid jet systems in which the fluid, typically water, is recirculated.
The fluid jet machining devices are frequently used to perform intricate and precise machining operations on solid materials like stone, masonry, steel and other metals. The devices employ high pressure pumps to supply water or another working fluid to a nozzle at pressures in the tens of thousands of pounds per square inch, while simultaneously providing a particulate abrasive such as garnet to the nozzle. The nozzle output is a fine, high-energy stream of the liquid and suspended abrasive. The stream, typically traveling at a velocity of several times the speed of sound, impinges upon a workpiece supported on a grate or other open-frame support structure. The workpiece is maintained stationery, while the nozzle guidance system dynamically controls the nozzle position and orientation relative to the workpiece to effect the desired machining operation.
Spent liquid and abrasive are collected in a reservoir positioned beneath the nozzle and workpiece. The larger abrasive particles tend to settle at and near the bottom of the reservoir, while smaller particles tend to remain suspended in the liquid. There are a variety of approaches to handling the spent liquid and abrasive, the simplest of which is to drain or pump away the liquid and particulate suspension, and shovel or otherwise remove the sediment as sludge or other solid waste. This approach involves considerable down time, and potential waste disposal problems, not only due to the abrasive but to workpiece particles and fragments that may include hazardous materials.
In an alternative approach, U.S. Pat. No. 6,299,510 (Massenburg) shows a fluid jet system in which water from the reservoir or catch tank is agitated by the stream from the nozzle to maintain more of the particulates in suspension, with the water then provided to a settling container. Water from the top of the settling container is relatively free of particles, and is circulated back to the catch tank. In a somewhat similar approach, published U.S. patent application Ser. No. 11/384,925 (Tirakian) shows a system in which a pump drawing water from a catch tank has a fluid collection housing, from which the water can be returned to the catch tank.
U.S. Pat. No. 6,328,638 (Hopkins et al.) discloses a fluid jet system with several recirculation stages, including a pre-classifier and a fine particle separation stage following the pre-classifier. Relatively clear water from each stage is recirculated to the catch tank.
U.S. Pat. No. 6,155,245 (Zanzuri) discloses a fluid jet cutting system with a fluid reservoir for collecting spent water and abrasive, noting that a drain for the reservoir in some instances can be connected to a fluid recycling structure to filter and pass the drained fluid back through the fluid pump and back into the nozzle to generate a continuous cutting cycle. While this is potentially advantageous from the standpoint of minimizing the need to supply outside water or other liquid to the system, the failure to provide extremely clean liquid to the high-pressure pump can damage the pump. In less severe cases, the water can accelerate wear to seals and other components to reduce the useful life of the pump.
Other pumps throughout the system, while not so sensitive as the high-pressure pump, are subject to severe wear when handling liquids laden with the larger abrasive particles and workpiece fragments. While filters can be employed at various stages to remove the coarser, larger-diameter particles, the periodic need to replace filters contributes to unwanted system down time.
Therefore, the present invention has several aspects, directed to one or more of the following objects:
to provide a fluid jet machining system in which spent abrasive, workpiece fragments, and other particulates are removed from the working liquid at minimal cost and with minimal disruption to the operation of the system;
to provide a system for removing the coarser, larger-diameter particles from the water or other working fluid recirculated in a fluid jet machining system, without exposing any of the pumps in the cycle to fluid laden with the coarser particles;
to provide a process for filtering finer, smaller-diameter particles from the working fluid in a fluid jet system while minimizing system down time; and
to provide a simple, low cost and reliable system for treating the working fluid for recirculation to the high-pressure pump in a fluid jet device.