Patent Publication Number: US-6220529-B1

Title: Dual pressure valve arrangement for waterjet cutting system

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to an improved system for delivery of ultra-high pressure water from a pump/intensifier to the nozzle of a waterjet cutting system, and more particularly to such a system which provides for a continuous flow from the pump/intensifier through the entire system and with nozzle discharge being at a pre-selected working pressure of either an ultra-high or a high pressure range. The arrangement of the present invention facilitates utilization of waterjet cutting systems for piercing operations on brittle or hard materials, as well as utilization of these systems on such materials without requiring cut-initiation from an outside edge of the workpiece. The features of the present invention will be discussed in detail hereinbelow. 
     Waterjet cutting systems are typically used for forming or cutting irregular or unusual patterns in dense and/or hard materials. Frequently, entrained abrasive is added to the discharge so as to provide a greater cutting force with the focused discharge stream of ultra-high pressure water from the nozzle. These systems are adapted for use in cutting or shaping brittle materials including metals, plastics and glass, including hardened glass as well as stone objects consisting of marble, granite or the like. Fragile materials are also uniquely suited for some types of ultra-high pressure waterjet cutting systems. 
     By definition, ultra-high pressure water systems typically utilize an operating pressure of at least 55,000 psi. In certain applications, pressures as high as 75,000 psi have been found useful as well. 
     In the operation of waterjet cutting systems, all components are subject to mechanical wear and require periodic maintenance and service. In a typical operational system, one component requiring an unusual amount of attention is the pump/intensifier. Maintenance problems are occasioned in significant part by the number of start-up cycles to which the pump/intensifier is subjected, rather than simply the time duration of operation. When subjected to less frequent start-ups, the overall life of a pump/intensifier between overhauls can be extended. The present invention facilitates operational cycles of longer duration, with the pump operating continuously under substantially the same high pressure conditions during the duration of these operational cycles. 
     In accordance with current practice, whenever it is desirable to change operational parameters such as cut location, or simply the introduction of fresh workpieces to the system, the operator typically de-energizes the pump/intensifier. By contrast, and in accordance with the present invention, the operator actuates a selector valve which is interposed between the pump/intensifier and the cutting nozzle, with this being a “T” valve and creating a normally open, continuously running lower working pressure bypass flow between the pump/intensifier and the cutting head. The bypass includes a pressure reducer in which the pressure of water passing through the bypass is dropped from the ultra-high level to a substantially lower but nevertheless working pressure level. Stated another way, in the line coupling the pump/intensifier to the cutting head a pressure reducer/bypass is interposed which is maintained in a normally open position during all periods of operation of the pump/intensifier. 
     The dual pressure selector valve arrangement enables constant operation of the pump/intensifier. Accordingly, the present invention employs a nozzle assembly and selector valve so as to deliver a constant stream of water entrained abrasive (if desired) to the surface of a workpiece at either of two significantly different working pressures. The system includes a cutting head capable of delivering water at a first ultra-high pressure in excess of about 55,000 psi, and also at a second somewhat reduced working pressures such as in the area of between about 5,000 and 55,000 psi. This arrangement makes it possible for the pump/intensifier to maintain continuous operation at the ultra-high pressure level for heavy duty cutting operations, without necessarily having to occasionally vary its operational parameters between ultra-high working pressure and a somewhat reduced but effective working pressure. 
     The ultra-high working pressure is utilized for conventional cutting applications, with the lower working pressure being utilized for initiating cuts or for piercing workpieces. This pressure reduction feature is particularly helpful when the workpiece consists of a brittle material such as glass, acrylics, some laminates, brittle metals and the like. The higher pressure working streams are prone to fracture the edges and/or the surfaces of the workpiece. In other words, the workpiece is better able to withstand forces from ultra-high working pressures as the cutting zone is ultimately moved inwardly from the peripheral edge, or when a piercing operation is completed. Since, the workpieces are better able to withstand forces from ultra-high working pressures and forces created from exposure to ultra-high working pressures once the workpiece has been completely pierced. 
     In accordance with the present invention, a selector valve arrangement is provided having an internal “T” arrangement in the head assembly. High pressure water enters the valve and passes into a three-way chamber with flow being controlled by a needle valve. In its closed position, the needle valve causes the water to pass through the channel leading to a series of cylindrical members with eccentric bores formed therein to create a drop in pressure, while at the same time permitting a modest flow rate to continue. This flow rate and operating pressure represent the lower of the two working pressures being delivered through the system. When ultra-high pressure is needed the needle valve is opened, whereupon flow of ultra-high pressure water passes through the main passageway and directly to the cutting head. The lower pressure line remains open during the entire operation, and in effect creates a parallel flow pattern without disruption of the coherent nature of the high pressure flow. 
     Therefore, it is the primary object of the present invention to provide an improved waterjet cutting system which employs a nozzle assembly provided with a means for delivering a stream of water or water with entrained abrasive onto a workpiece at two significantly different working pressures, with the pump/intensifier operation being uninterrupted. 
     It is a further object of the present invention to provide an improved waterjet cutting system which permits continuous operation of a pump/intensifier while delivering water entrained abrasive to a workpiece at either one of two selected working pressures, with one of the working pressures being an ultra-high pressure, and with the other being at a reduced but yet effective working or cutting pressure. 
     It is yet a further object of the present invention to provide a waterjet cutting system which permits the pump/intensifier to maintain operation continuously while cutting operations are undertaken at either of two selected working pressures. 
     It is still a further object of the present invention to provide an improved waterjet cutting system designed to initiate cuts and/or piercing of workpieces through the utilization of a pressure reduction feature which permits the discharge of water entrained abrasive at working pressures significantly less than ultra-high working pressures employed for normal cutting. 
     Other and further objects of the present invention will become apparent to those skilled in the art upon a study of the following specification, appended claims and accompanying drawings. 
    
    
     IN THE DRAWINGS 
     FIG. 1 is a schematic diagram of a waterjet cutting system arranged in accordance with the present invention; 
     FIG. 2 is a detail elevational view of the selector valve as employed in the present invention; 
     FIG. 3 is a sectional view taken through the diameter of the selector valve as illustrated in FIG. 2, and illustrating the detail of the pressure reducer; and 
     FIG. 4 is a detail sectional view of a fragmentary portion of the selector valve, with the portions being cut away, and illustrating the arrangement of the internal arrangement of the selector valve and pressure reducer components. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     In accordance with the preferred embodiment of the present invention, and with particular attention being directed to FIG. 1 of the drawings, the waterjet cutting system generally designated  10  includes an abrasive hopper  11  with a discharge conduit as at  12  delivering abrasive into a metering arrangement as in  13 . Abrasive is delivered to conduit  14  directly to the cutting head  15 . Ultra-high pressure water is supplied through pump/intensifier  17 , and delivered along delivery conduit  18  to pressure control or selector valve  19 . Selector valve  19  is controlled by pressure selector control  20 . Abrasive may alternatively be delivered in accordance with the system disclosed in copending application Ser. No. 09/237,582, filed Jan. 26, 1999, entitled “ABRASIVE DELIVERY SYSTEM”, and assigned to the same assignee as the present invention. Ultra-high pressure water enters selector valve  19  through inlet  21 , with valve  19  providing a constant flow of water to the outlet at a reduced pressure to a bypass arm through outlet  22  and on to cutting head  15 . When selector valve  19  is open, ultra-high pressure water flows from outlet  24  to conduit  25  to inlet  26  of cutting head  15 . The details of cutting nozzles are known such with one typical cutting nozzle being disclosed in U.S. Pat. 5,018,670 dated May 28, 1991 and entitled “CUTTING HEAD FOR WATERJET CUTTING MACHINE”; and U.S. Pat. No. 5,851,139 dated Dec. 22, 1998, titled “CUTTING HEAD FOR A WATERJET CUTTING ASSEMBLY” and assigned to the same assignee of the present invention. 
     For overall control of the system, a compressed air source provided as at  28 , and delivers flow of air to abrasive control  29  as well as to control valve  20  functioning with selector valve  19 . 
     In the arrangement illustrated in FIG. 1, a working stream of water is delivered to head  15  through the normally open channel to outlet  22  of selector valve  19 . This flow makes up the reduced pressure working stream and due to the normally open disposition of outlet  22 , this flow occur is ongoing at all times. At the same time, selector control  30  is provided to controllably open or close a needle valve disposed within selector valve  19  so as to either permit or prevent a flow of ultra-high pressure water from the pump/intensifier  17  through valve  19  and thence through line  25  to cutter head  15 . Also, abrasive delivery control  29  permits a flow of metered abrasive along conduit  14  to cutter head  15  so as to enhance the cutting capability of the abrasive/water working stream delivered from nozzle  15  as at  32 . 
     With attention now being directed to FIG. 2 of the drawings, control valve  19  comprises a valve body as at  35 , with this being a three-way valve having one normally open channel through the bypass link  36  through which a working stream of water at slightly reduced but yet effective working pressure is permitted to flow. Conduit  25  delivers ultra-high pressure water from valve  19  to cutter head  15 , as previously indicated and discussed in connection with FIG.  1 . 
     With attention now being directed to FIG. 3 of the drawings, it will be observed that valve  19  is provided with a control mechanism generally designated  40  which operates through the application of compressed air along line  41  couples directly to mechanism  40 . Needle valve  42  is disposed axially within bore  43  so as to control flow through the “T” section generally designated  44 . Ultra-high pressure water enters valve  19  as at a bore or orifice  46 . With needle valve  42  in closed disposition (as shown) the flow of ultra-high pressure water continues through bore  47  into the pressure reducing assembly shown generally at  48 . 
     Pressure reducing assembly  48  includes a cylindrical body member having a bore  50  formed therewithin, with bore  50  including a plurality of axially aligned serially disposed pressure reducing spools or sleeves such as at  51 — 51 . Spools  51  are provided with eccentric bores as at  52  to permit a continuous flow of water through these eccentrically disposed channels with pressure reduced from the ultra-high pressure, water is discharged from pressure reducer  48  at  55 . Flow then continues through line  36  to “T” fitting  57 , and thence through discharge  58  into conduit  25 . 
     With attention now being directed to FIG. 4 of the drawings, the working stem of needle valve  42  is illustrated in its closed or seated position, with the stem portion extending through seal packing  60 . Individual cylinders forming the pressure reducing spools  51  are also illustrated, with the eccentric flow channels such as at  52  having a proximal basin-like zone or opening  60 A formed at one end. Basin  60 A is sufficiently large in diameter so as to fully encompass next adjacent eccentric channel in the next or succeeding spool, such as shown in FIG. 4 at  52 A. 
     With continued attention being directed to FIG. 4, it will be observed that when needle valve  42  is lifted from seat  61 , ultra-high pressure water will flow along the line and in the direction of arrow  62 , and onto conduit  25  for delivery to cutting head  15 . In other words, when needle valve  61  is in its open disposition, the stream of ultra-high pressure water utilized to form the ultra-high working pressure stream passes along the line and in the direction of the arrow  62 . When needle valve  61  is seated, there is a constant and ongoing flow of water along the line and in the direction of the arrow  63  for entry into the pressure reduction component of the system. 
     In a typical operational mode, the volume of ultra-high pressure water passing through the pressure reduction/bypass arm will be between about 10% and 15% of the overall volume being carried, particularly during the time that ultra-high pressure water is not being delivered through the cutting nozzle. Under operational conditions, and with ultra-high pressure water flowing only through the pressure reduction/bypass arm, the working pressure at the nozzle is normally between about 5000 and 20,000 psi, and preferably at 12,000 psi. In a specific mode, with selector valve open and when the pressure at the cutting nozzle is 20,000 psi, a typical volume rate of flow is 15% of the flow with ultra-high pressure water flowing to the nozzle. 
     It will be appreciated, therefore, that the present invention provides a system in which a working stream of water entrained abrasive may be delivered to a workpiece to significantly different working pressures. The system provides for the utilization of a cutting head capable of delivering a working stream at an ultra-high working pressure in excess of 55,000 to 80,000 psi while at the same time being capable of delivering a second extreme of somewhat reduced working pressure such as in the area from between 5,000 and 20,000 psi. Actuation of a single valve enables the conversion from one of the working pressures to the other. Thus, continuous operation and actuation of the pump/intensifier for the system is possible so as to enable operation of the system on a substantially continuous basis. Accordingly, it is possible to initiate edge cuts as well as piercing operations at one working pressure, while continuing and maintaining operation of the system at the desired ultra-high working pressure for higher speed cutting operations. 
     It would be appreciated that the features of the present invention as disclosed herein are for purposes of illustration only, and are not to be construed as a limitation upon the scope of the following appended claims.