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Title: Pneumatic fail-safe sensor system for N/C machine tool
Claims: The embodiments of the invention in which an exclusive property or privilegeis claimed are defined as follows: 1. In an N/C machine tool, adapted to cut a part in accordance with a program that includes a probe adapted to follow a master pattern as the part is being cut, the improvement comprising a pneumatic sensor system, said pneumatic sensor system including: a pneumatic valve mechanism including a movable element and a valve seat, said movable element adapted to open and close an aperture formed in said valve seat; a probe connected to said movable element and normally spaced from said master pattern, said probe adapted to contact said master pattern whenever said N/C machine deviates from the cutting path established by said program, said probe being displaced when it comes in contact with said master pattern, said master pattern probe contact causing said movable element of said valve mechanism to be displaced and open said aperture formed in said valve seat; a pneumatic pressure source for applying pneumatic pressure to said aperture in said valve seat; pneumatic pressure sensing means for sensing drops in the pneumatic pressure applied to said aperture in said valve seat, said pneumatic pressure drops occurring when said movable element of said pneumatic valve mechanism is displaced by said probe coming in contact with said master pattern; and, electronic control means connected to said pneumatic pressure sensing means for detecting when said pneumatic pressure sensing means detects a drop in the pneumatic pressure applied to said aperture in said valve seat and generating control signals suitable for terminating the operation of said N/C machine tool in a rapid manner when a said pneumatic pressure drop is detected. 2. An improved N/C machine tool as claimed in claim 1 wherein said pneumatic valve mechanism also includes a dome having an open end, said valve seat being attached to said open end of said dome in a manner such that said movable valve element is located in said dome; and, including first conduit means for connecting said dome to said pneumatic pressure source so that said dome becomes pressurized, said dome pressure pressing said movable valve element against said valve seat to close said aperture in said valve seat. 3. An improved N/C machine tool as claimed in claim 2 wherein said probe includes a passageway which terminates in at least one aperture formed in the end of said probe remote from said movable valve element; and, including second conduit means for connecting said passageway to said pneumatic pressure source in a manner such that gas under pressure is emitted from said at least one aperture formed at said end of said probe remote from said valve element. 4. An improved N/C machine tool as claimed in claim 3 wherein said second conduit includes a helical portion located in said dome. 5. An improved N/C machine tool as claimed in claim 4 wherein said movable valve element comprises a valve plate having an annular projection and wherein said aperture in said valve seat is an annular groove closed by said valve plate annular projection. 6. An improved N/C machine tool as claimed in claim 5 wherein said valve mechanism includes an elongated valve stem having a longitudinal axis, said valve plate being attached to one end of said valve stem, said valve stem extending through said valve seat, said probe affixed to the end of said valve stem remote from the end to which said valve plate is attached so as to lie along said longitudinal axis. 7. An improved N/C machine tool as claimed in claim 6 including a chuck attached to said remote end of said valve stem, said probe being held in said chuck. 8. An improved N/C machine tool as claimed in claim 7 wherein said valve seat mates with said dome along a spherical mating surface; and, including adjustment cap screws adapted to attach said valve seat to said dome in a manner such that the positioning of said cap screws positions said valve seat, said valve seat position, in turn, positioning said valve stem and said probe. 9. An improved N/C machine tool as claimed in claim 8 including a valve stem guide block mounted in a centrally located aperture formed in said valve seat about said longitudinal axis, said valve stem guide block including a central aperture also located along said longitudinal axis; and, wherein said valve stem includes a peripheral projection formed and positioned so as to impinge on said central aperture formed in said valve stem guide block and act as a fulcrum point for said valve stem. 10. An improved N/C machine tool as claimed in claim 9 wherein said electronic control means includes a low voltage section and a high voltage section. 11. An improved N/C machine tool as claimed in claim 10 wherein said low voltage section comprises: a touche detector connected to said pressure sensing means for detecting when said pressure sensing means detects that said valve plate has been moved and generating an output in accordance therewith; a touche latch connected to the output of said touche detector and latched when said touche detector generates an output indicating that said pressure sensing means has detected that said valve plate has moved; and an optical isolator connected to the output of said touche latch for sensing when said touche latch is latched. 12. An improved N/C machine tool as claimed in claim 11 wherein said N/C machine is AC energized and wherein said high voltage section comprises: a zero crossing detector/trigger connected to the output of said optical isolator for generating a trigger signal when said optical isolator senses that said touche latch is latched and the AC voltage energizing said N/C machine passes through zero; and, a thyristor control connected to the output of said zero crossing detector so as to be activated when said zero crossing detector/trigger generates a trigger signal, said thyristor control being connected to the blocking valves of said N/C machine tool to activate said blocking valves when said thyristor is activated by said trigger signal. Other info: Inventors: MacSpadden, Floyd E. (Kent, WA, US) Schellhase, Frank A. (Issaquah, WA, US) Strong, Robert L. (Auburn, WA, US) Tieden, Jansey D. (Puyallup, WA, US) Application Number: 518090 Filing Date: 1974-10-25 Publication_date: 1976-11-16 Assignee: The Boeing Company (Seattle, WA) Primary Class(es): 409/80 409/126, 409/137 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Simpson, Othell M. Assistant Examiner: Briggs, W. R. Attorney: Christensen, O'Connor, Garrison & Havelka |
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