Abrading – Machine – Sandblast
Reexamination Certificate
1999-01-26
2001-03-13
Rachuba, M. (Department: 3724)
Abrading
Machine
Sandblast
C451S100000
Reexamination Certificate
active
06200203
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an improved liquid/abrasive jet material cutting system, and more particularly to such a system which provides an improved arrangement for the introduction and/or injection of abrasive particles into the stream of high pressure liquid forming the jet. More specifically, the present invention relates to an improved delivery system for controllably, accurately, and reliably introducing abrasive to a cutting head through which water is being passed for use in creating a liquid/abrasive jet intended for material cutting operations.
High pressure water is frequently utilized in operations for forming cuts in hard or brittle material, and also for the formation of cuts involving unusual or difficult-to-machine patterns. The utilization of water jets for such operations have proved to be highly effective and desirable. In improving these systems for enhancing the utility, speed and effectiveness of the water jets for a variety of applications, abrasive particulate is injected into the fluid flow. However, it is frequently difficult to appropriately and effectively meter the flow of such particulate to the cutting heads, and the present invention provides a system for rendering the metering of such delivery more reliable and effective.
Abrasive delivery systems perform the function of storing and conveying the abrasive particles over varying distances from the storage site for the introduction to the jet. The conveying function is normally achieved through the use of a pneumatic drive. When long distances are involved for the transfer of the abrasive to the jet system, problems may be encountered at the delivery site. In order to more effectively control the flow and hence the delivery, various metering systems have been proposed and utilized. However, present metering systems have not proven to be effective and reliable over periods of time, and improvements are desirable. The present delivery system has proven effective in improving both reliability and accuracy of the delivery system. When so undertaken, the versatility and adaptability of water jet cutting systems is enhanced, and the abrasive-ladened water jet provides a means for cutting through virtually any known material.
SUMMARY OF THE INVENTION
In delivery of abrasive, both fluidized systems as well as solid-phase systems have been employed. The present invention involves an improved solid-phase delivery with a pressurized primary hopper being used to supply an ongoing flow of abrasive to the cutting head or heads. Since working configurations involve single and/or multiple cutting heads, and since each cutting head normally requires individual and separate control, a predetermined abrasive flow through the system to each head may require additional means to maintain and equalize abrasive flow. In this connection, and in accordance with the present invention, a secondary hopper is provided in the delivery tube from the primary hopper, with the features of the secondary hopper providing accurate metering along with reliable on/off control of the abrasive flow. A gate such as a pneumatically actuated slide gate may be provided in order to create reliable on/off control of the abrasive flow. Thus, when the slide gate is opened, abrasive is permitted to fall through a rate control or flow metering means and thence into the cutting head where it is mixed with a flow of high pressure water for creating the actual jet stream. As a further feature of the present invention, the metering means may comprise a rotatable wheel or disc having various sized holes or bores that permit and facilitate change to achieve the desired rate of flow of abrasive to the cutting head.
Therefore, in accordance with the present invention, a liquid/abrasive jet material cutting system is provided which incorporates a suitable pump providing a source of high pressure water or other liquid. A source of abrasive particles is provided which incorporates primary and secondary hoppers, with the primary hopper providing a reservoir and source for abrasive particles which becomes blended in or mixed with the high pressure cutting liquid. The abrasive particulate is conveyed pneumatically from the primary hopper to the secondary hopper, with the secondary hopper serving the dual function of relieving pneumatic pressure build up from the pneumatic conveyor, along with accurately metering the flow of abrasive particulate to the cutting head. In this connection, the flow of abrasive particles is normally directed to a mixing chamber in the cutting head for delivering the coherent high velocity working liquid stream to the surface of the workpiece. The schematic diagram of
FIG. 1A
illustrates the configuration and/or working arrangement of the major components of a liquid/abrasive jet material cutting system employing the present invention.
The secondary hopper of the present invention is typically in the form of an elongated vessel which defines an enclosure with opposed end walls having an inlet port formed in one end wall and an outlet port in the opposed end wall. An annular divider plate is interposed in the enclosure between the end walls so as to define a pair of chambers including an inlet chamber and an outlet chamber. An orifice is formed in the divider plate for controlling gravitational flow of abrasive particulate from the inlet chamber to the outlet chamber, and also to provide a floating air lock between the inlet and outlet chambers. Since the flow of abrasive from the primary hopper is normally propelled by compressed air, the inlet chamber is generally exposed to a pressure determined primarily by the pneumatic conveyor system. Since this elevated pressure may vary from time to time, depending upon flow conditions, the inter positioning of an air lock has been found to enhance accuracy, consistency and reliability of the abrasive delivery system. The outlet chamber is vented to atmosphere, and hence when the floating air lock is in its open configuration, pressure is relieved from the inlet chamber and the rate of flow into the inlet chamber may be increased. Conversely, when the floating air lock is in its closed configuration, the rate of transfer of compressed air from the inlet chamber to the outlet chamber is retarded, and thus the pressure is free to rise within the inlet chamber, thereby automatically reducing flow of particulate.
The floating air lock is created by positioning a delivery tube in the divider plate, with the delivery tube extending downwardly a finite distance into the outlet chamber. In this arrangement, abrasive particles are transferred from the inlet chamber to the outlet chamber where they free-fall and form a part of a rising column. When it reaches a predetermined height within the outlet chamber, this column of particulate creates an in-situ air lock so as to effectively isolate the inlet and outlet chambers, while permitting constant venting of the outlet chamber to atmosphere. The outlet chamber of the secondary hopper is coupled to a delivery conduit which leads to and is in communication with the mixing chamber of the delivery nozzle from which the working mixture is discharged.
In this arrangement, therefore, the dual hopper system provides effective means of delivering a consistent and controllably regulated flow of abrasive particles to cutting heads, and at the same time provides a means for accommodating the delivery of particulate to the cutting heads under low or atmospheric pressure.
Therefore, it is a primary object of the present invention to provide an improved abrasive delivery system for controllably and reliably metering the flow of abrasive particles into a flow of ultra high pressure liquid for liquid/abrasive jet cutting systems.
It is a further object of the present invention to provide an improved delivery system for conveying abrasive particles from a hopper source in a flow for mixing of the abrasive with ultra high pressure water for the purpose of performing liquid/abrasive jet cutting operations.
It is still a further
Lague Jude
Otterstatter Kevin D.
Xu Ji-an
Haugen Law Firm PLLP
Jet Edge Division of TM/American Monorail, Inc.
Rachuba M.
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