Abstract:
A thermal energy machining (“TEM”) machine gas handling system in which the improvement is a fluid-controlled pressure regulation subsystem for controlling the dispensing of a TEM process gas via the regulation of the pressure of the TEM process gas. Such subsystems include a pressure regulator, a pressure transducer, and a digital controller working in combination to control the process gas outlet pressure of the pressure regulator. The pressure regulator&#39;s diaphragm that controls the valve that regulates the process gas outlet pressure is mechanically acted upon by the piston of a pneumatic or hydraulic cylinder. Controlling the pneumatic or hydraulic cylinder regulates the output pressure of the process gas. The pressure transducer and the digital controller work in combination to adjust the feed pressure of the pneumatic or hydraulic cylinder, which in turn regulates the pressure of the process gas at the outlet of the pressure regulator.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to thermal energy machining (“TEM”) machine gas handling systems having improved a fluid-controlled pressure regulation subsystem for controlling the dispensing of at least one of the TEM process gases. 
       DESCRIPTION OF THE RELATED ART  
       [0002]    TEM was introduced in the late 1960&#39;s as an effective way to remove internal and external burrs and flashing from machined or molded metal and plastic parts. TEM is also known “gas detonation deburring,” “thermal deburring,” “combustion chamber treatment,” and “rapid high energy removal of superfluous projections.” The concept behind TEM is elegantly simple: instead of mechanically abrading off burrs and flashing, the burrs and flashing are simply burned away in a fraction of a second. This simple concept is applied in an exciting way: one or more metal or plastic parts requiring deburring or deflashing are sealed inside a combustion chamber and surrounded with a highly pressurized explosive gas mixture which is then ignited by an electric spark. The resulting explosion produces a thermal shock wave that literally burns away (oxidizes) the burrs and flashings from the parts while the relatively great thermal mass of the parts prevents the parts themselves from being damaged by the thermal shock wave. The explosive flame temperature can reach over 6,000° F. (3,316° C.). The explosion lasts only milliseconds and the entire load-to-load cycle time is on the order of half a minute. Descriptions of various aspects of TEM are found in U.S. Pat. No. 3,475,229, to Geen et al.; U.S. Pat. No. 3,666,252 to Rice; U.S. Pat. No. 3,901,488 to Riddle; U.S. Pat. No. 3,992,138 to Leisner; U.S. Pat. No. 3,994,668 to Leisner et al.; U.S. Pat. No. 4,025,062 to Johnstone et al.; U.S. Pat. No. 4,094,339 to Leisner et al.; U.S. Pat. No. 4,394,007 to Leisner; U.S. Pat. No. 4,394,334 to Kiss; U.S. Pat. No. 4,474,547 to Drexel et al.; U.S. Pat. No. 4,486,173 to Hieber et al.; U.S. Pat. No. 4,487,576 to Martini; U.S. Pat. No. 4,543,570 to Bressert et al.; U.S. Pat. No. 4,561,839 to Neumann; U.S. Pat. No. 4,595,359 to Conrad et al.; U.S. Pat. No. 4,712,998 to Conrad; U.S. Pat. No. 4,721,458 to Conrad; U.S. Pat. No. 4,740,152 to Conrad; U.S. Pat. No. 4,760,630 to Conrad et al.; U.S. Pat. No. 4,796,868 to Bozhko et al.; U.S. Pat. No. 4,819,917 to Cherendin et al.; U.S. Pat. No. 4,826,541 to Bozhko et al.; U.S. Pat. No. 4,925,499 to Wohr; U.S. Pat. No. 6,713,016 B2 to Kaercher et al.; and in U.S. Pat. Pub. Nos. US 2006/0192327 A1 of La Gala; US 2007/0221875 of Conrad; Great Britain Pat. No. 1 525 633 to Robert Bosch GmBH; and Patent Cooperation Treaty International Pat. Pub. No. WO 2008/019934 A1. 
         [0003]    The explosive gas mixture typically comprises two process gases: one is an oxygen-source gas, usually oxygen, and the other is a fuel gas, e.g., hydrogen, methane, natural gas or a mixture thereof. Both the composition and mass of the gas mixture in the explosion chamber are critical to the success of the TEM process. The optimal gas mixture composition and the gas mixture amount for a given load of parts varies with the number, size, configuration, and material of the parts being treated. Precise metering of the process gases is used to achieve a desired mixture composition and to control the overall mass of the gas mixture in the combustion or explosion chamber. Too much of a gas mixture, even of the correct mixture composition, can result in an explosion that exceeds the safe operational conditions of the TEM machine. 
         [0004]    The composition of the gas mixture may be determined by the mass ratio of the component process gases. Under the ideal gas law, the mass of a gas is proportional to its pressure for a predetermined volume and temperature. Thus, the mass ratio of the process gases can be controlled by controlling the pressures of the process gases either (1) directly entering the combustion chamber of the TEM machine, or (2) entering a fixed volume dosing device that is used to dose the gas into the combustion chamber. Accordingly, it is known in the art to adjust the respective pressures of the process gases to optimize the TEM process for the particular number, size, and material of the parts being treated. 
         [0005]    Various methods have been used in the art to control the pressures of the process gases. The least sophisticated way to do this is to manually adjust output pressures of gas regulators for the process gases. More sophisticated ways have been developed over the years. For example, U.S. Pat. No. 4,721,458 to Conrad teaches using an automated feedback control system to control an electric drive system to dynamically adjust the diaphragm of a gas pressure regulator for one of the process gases and thereby control the output pressure of the pressure regulator. However, the electric drive systems have electric components in proximity to the areas in which flammable gases of the TEM process are used and so pose a risk of causing an unwanted explosion. What is needed is a safer automated system for controlling the pressures of the process gases in the TEM process. 
       SUMMARY OF THE INVENTION  
       [0006]    The present invention provides an inherently safer system for controlling the pressures of the process gases in the TEM process than do the prior art systems which employ electric drives to control the diaphragm of a process gas pressure regulator. The present invention provides a TEM gas handling system in which the improvement is a fluid-controlled pressure regulation subsystem for controlling the dispensing of at least one of the TEM process gases via the regulation of the pressure of the TEM process gas either (1) directly to the combustion chamber or a mixing block or (2) indirectly to the combustion chamber or a mixing block by way of a fixed volume dosing device. 
         [0007]    Such fluid-controlled pressure regulation subsystems include a pressure regulator, a pressure transducer, and a digital controller working in combination to control the process gas outlet pressure of the pressure regulator. In these subsystems of the present invention, the pressure regulator&#39;s diaphragm that controls the gas flow valve that regulates the process gas pressure at the pressure regulator outlet is mechanically acted upon by the piston of a pneumatic or hydraulic cylinder. Thus, by controlling the pneumatic or hydraulic cylinder, it is possible to regulate the output pressure of the process gas. The present invention employs the pressure transducer and the digital controller in combination to adjust the feed pressure of the pneumatic or hydraulic cylinder, which in turn regulates the process gas at the outlet of the pressure regulator. Thus, in contrast to the pressure regulation subsystem taught by U.S. Pat. No. 4,721,458 to Conrad, the pressure regulator of the present invention requires no electrical parts and therefore reduces the risk of an explosion occurring in that part of the TEM machine. 
         [0008]    The present invention also includes TEM machines having the aforementioned improvements. Such TEM machines may also include a processing parameter electronic database containing process gas target pressure data for various part load characteristics, e.g., size, number, material type, etc., that can be used to control the process gas outlet pressure of the subsystem pressure regulators. Thus, according to one aspect of the present invention, a TEM machine operator may input the characteristics of the part load into an input device that electronically communicates with the database via a process controller to provide the subsystem digital controller with the target process gas output pressure at the pressure regulator and thereby automatically control the results of the TEM process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]    The criticality of the features and merits of the present invention will be better understood by reference to the attached drawings. It is to be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the present invention. 
           [0010]      FIG. 1  is a schematic representation of a TEM machine according to an embodiment of the present invention. 
           [0011]      FIG. 2 . is a schematic representation of a pneumatic-controlled pressure regulation subsystem for controlling the dispensing of at least one of the TEM process gases according to an embodiment of the present invention. 
           [0012]      FIG. 3  is a schematic representation of a cross-section of a pressure regulator that is a component of the embodiment of the present invention shown in  FIG. 2 . 
           [0013]      FIG. 4  is a schematic representation of a portion of a control system of a TEM machine in accordance with an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    In this section, some preferred embodiments of the present invention are described in detail sufficient for one skilled in the art to practice the present invention. It is to be understood, however, that the fact that a limited number of preferred embodiments are described herein does not in any way limit the scope of the present invention as set forth in the appended claims. 
         [0015]    Referring to  FIG. 1 , there is shown a schematic representation of a TEM machine  100  in accordance with an embodiment of the present invention. The TEM machine  100  comprises a fuel gas handling system  102 , an oxygen gas handling system  104 , a mixing block  106 , an ignition source  108 , a combustion chamber  110 , and an exhaust gas system  112 . The fuel gas handling system  102  comprises a high pressure fuel gas source  114 , a fuel gas pressure regulation subsystem  116 , and a fuel gas dosing device  118 . Similarly, the oxygen gas handling system  104  comprises a high pressure oxygen gas source  120 , an oxygen gas pressure regulation subsystem  122 , and an oxygen gas dosing device  124 . The direction of gas flow is shown by the arrows between the components, e.g., arrow  126 . 
         [0016]    In operation, the machined or injection molded parts that are to be deburred or deflashed are loaded into the combustion chamber  110  and the combustion chamber  110  is sealed. The atmosphere within the combustion chamber  110  may be evacuated/backfilled or purged to establish standard starting atmospheric conditions. (The subsystem of the TEM machine used to establish standard starting conditions is not identified in  FIG. 1 ). The fuel gas handling system  102  is operated to provide the fuel gas that is needed to treat the parts within the combustion chamber  110 . The fuel gas flows from the fuel gas source  114  to the fuel gas pressure regulator subsystem  116 . The fuel gas pressure regulator subsystem  116  regulates the pressure of the fuel gas flowing to the fixed volume fuel gas dosing device  118  to fill the fuel gas dosing device  118  with the predetermined mass of fuel gas that is needed for processing the parts. Similarly, the oxygen gas flows from the oxygen gas source  120  to the oxygen gas pressure regulator subsystem  122 . The oxygen gas pressure regulator subsystem  122  regulates the pressure of the oxygen gas flowing to the fixed volume oxygen gas dosing device  124  to fill the oxygen gas dosing device  124  with the predetermined mass of oxygen gas that is needed for processing the parts. The fuel gas and oxygen gas dosing devices,  118 ,  124  are simultaneously operated to inject their gases into the mixing block  106  to intimately mix the gases en route to the combustion chamber  110 . When the combustion chamber  110  becomes filled with the requisite amounts of the fuel gas/oxygen gas mixture, the ignition source  108  is operated to explode the gas mixture. The explosion instantly burns away the burrs and/or flashings that are present on the parts. The excess pressure of the combusted gas mixture is released through the exhaust gas system  112  and the combustion chamber  110  is opened it to remove the deburred/deflashed parts. 
         [0017]    Referring now to  FIG. 2 , a preferred embodiment of a pneumatically-controlled pressure regulation subsystem  130  for controlling the dispensing of either the fuel gas or the oxygen gas via regulation of the process gas pressure is shown schematically using standard I.S.O. symbols. The pressure regulation subsystem  130  shown in  FIG. 2  corresponds separately to the fuel gas pressure regulation subsystem  116  and the oxygen gas pressure regulator subsystem  122  of  FIG. 1 . The pressure regulation subsystem  130  comprises a pressure regulator  132 , a pressure transducer  134 , and a digital controller  136 , which work in combination to control the process gas outlet pressure of the pressure regulator  132 . As is described in more detail below, the pressure regulator  132  includes a regulator body  138  which is operationally connected to a linear cylinder  140 . The linear cylinder  140  is supplied with pneumatic power from a source (not shown in  FIG. 2 ), e.g., of compressed air, via a supply line  142  by way of a directional valve  144  and a proportional valve  146 . 
         [0018]    In operation, the process gas from the gas source, e.g., the fuel gas source  114  or the oxygen gas source  120  of  FIG. 1 , flows into the regulator body  138  via the input line  148  and out of it through the output line  150 . The pressure transducer  134  is located on the output line  150  and senses the process gas output pressure from the pressure regulator  132 . The pressure transducer  134  is in electronic communication with the digital controller  136 , as is depicted by input communication line  152  (which can be a wire or a wireless communication line), to signal the output process gas pressure to the digital controller  136 . The digital controller  136  determines whether or not the output pressure corresponds to a predetermined target pressure value and sends appropriate output signals to the directional valve  144  and the proportional valve  146  (as depicted by output communication lines  154 ,  156 , which can be wire or wireless communication lines) so as to cause the linear cylinder  140  to adjust a diaphragm/valve combination (not shown in  FIG. 2 ) in the regulator body  138  to achieve a target output pressure. The pressure adjustment loop continues until it is determined that the predetermined mass of gas has been provided to the relevant dosing device, e.g., fuel gas dosing device  118  or oxygen gas dosing device  124  of  FIG. 1 . 
         [0019]    It is to be understood that a single digital controller may be used as part of the pressure regulation subsystems of all of the process gases, or each subsystem may have its own digital controller. Also, the digital controller(s) may be part of an overall process control processor of the TEM machine or it (they) may be separate from such an overall process controller. 
         [0020]    Referring now to  FIG. 3 , there is shown a schematic representation of a gas pressure regulator  160  according to an embodiment of the present invention. The pressure regulator  160  comprises a regulator top  162  and a linear cylinder  164 . The regulator top  162  has a poppet valve  166  functionally interposed between a gas inlet  168  and a gas outlet  170 . The regulator top  160  also has a diaphragm  172  in mechanical communication with the poppet valve  166  so that the flexure state of the diaphragm  172  controls the state of openness of the poppet valve  166 . The linear cylinder  164  comprises a cylinder  174 , a piston  176  moveably disposed therein, and at least one port (not shown in  FIG. 3 ) for the ingress/egress of a control fluid, e.g., compressed air. The piston  176  is in mechanical communication with the underside of the diaphragm  172  so that the position of the piston  176  within the cylinder  174  controls the flexure state of the diaphragm  172 . 
         [0021]    In operation, a process gas flows into the gas regulator  160  via gas inlet  168 , through poppet valve  166  and out of the gas regulator  160  via gas outlet  170 . As is known by those skilled in the art, by controlling the rate of flow through the gas regulator  160 , poppet valve  166  effectively controls the output pressure of the gas exiting through gas outlet  170 . Because the openness state of poppet valve  166  is controlled by the flexure state of the diaphragm  172 , which in turn is controlled by the position of the piston  176  within cylinder  174 , the process gas output pressure of regulator  160  is controlled by controlling the operation of the linear cylinder  164 . 
         [0022]    It is to be specifically understood that although the valve that is positioned between the process gas inlet  168  and outlet  170  of the pressure regulator  160  is depicted in  FIG. 3  as a poppet valve  166 , the valve may be of any type known in the art is operable in conjunction with a pressure regulator diaphragm. 
         [0023]    The present invention also includes TEM machines having an electronically-accessible processing parameter database containing process gas target pressure data for various part load characteristics, e.g., size, number, material type, etc., that can be used to control the process gas outlet pressure of the subsystem pressure regulators. Refer to  FIG. 4 , which shows a schematic representation of the database/pressure regulation system interaction. By using such a database  180 , a TEM machine operator can automatically control the results of the TEM process by inputting the characteristics of the part load into a data processor  182  either by wire or wirelessly via an input device  184 . The data processor  182  electronically communicates by wire or wirelessly with the database  180  to obtain data regarding the target gas output pressure value for the process gas pressure regulators of the respective fluid-controlled pressure regulation subsystems, e.g., fluid-controlled pressure regulation subsystem  186 . The data recovered may be the relevant target pressure values, data from which the relevant target pressure values may be calculated, one or more algorithms for calculating the target pressure values, or any combination thereof. The data processor  182  subsequently communicates the target pressure value information by wire or wirelessly to the digital controller of the relevant fluid-controlled pressure regulation subsystem  186 . The digital controller then controls its related process gas regulator to output the relevant process gas at the target pressure. 
         [0024]    In TEM machines of some embodiments of the present invention, an overall process control processor or computer is used to control and/or monitor the operation of the TEM machine. In such embodiments, the database  180  and input device  184  may be associated with or part of such an overall process control processor. Likewise, in some embodiments the data processor  182  may be the overall process control processor or a part thereof. 
         [0025]    While only a few embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that many changes and modifications may be made thereunto without departing from the spirit and scope of the present invention as described in the following claims. All patent applications and patents, both foreign and domestic, and all other publications referenced herein are incorporated herein in their entireties to the full extent permitted by law.