Abstract:
A remote vacuum or pressure sealing apparatus and method for making a radiation tolerant, remotely prepared seal that maintains a vacuum or pressure tight seal throughout a wide temperature range. The remote sealing apparatus includes a fixed threaded sealing surface on an isolated system, a gasket, and an insert consisting of a plug with a protruding sample holder. An insert coupling device, provided for inserting samples within the isolated system, includes a threaded fastener for cooperating with the fixed threaded sealing surface on the isolated system. The insert coupling device includes a locating pin for azimuthal orientation, coupling pins, a tooted coaxial socket wrench, and an insert coupling actuator for actuating the coupling pins. The remote aspect of the sealing apparatus maintains the isolation of the system from the user&#39;s environment, safely preserving the user and the system from detrimental effect from each respectively.

Description:
The United States of America may have certain rights to this invention under Management and Operating contract No. DE-AC05-06OR23177 from the Department of Energy. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to achieving a vacuum or pressure tight seal on an isolated system and more particularly to a device and method for making a radiation tolerant, remotely prepared seal that maintains a vacuum or pressure tight seal. 
     BACKGROUND OF THE INVENTION 
     In particle accelerators, nuclear power plants, chemical plants and the like, it is sometimes necessary to introduce a material into a hazardous or controlled environment remotely to insure the protection of personnel from the hazardous environment. A controlled environment could include sealed areas that are under vacuum or pressure or which contain hazardous materials such as chemicals or radioactive substances. 
     At the Jefferson National Lab, for example, in the electron beam line, the electron beam is typically maintained in a high vacuum and at ultra-low temperature to maintain a superconducting operation. The high vacuum in the beam line is typically maintained at below 1×10− 9  Torr. Some portions of the beam line are cooled with liquefied helium that has been chilled to 456 degrees below zero Fahrenheit, nearly Absolute Zero, to keep the acceleration cavities cold. 
     In order to carry out electron-proton scattering experiments, materials are often inserted directly into the path of the relativistic particles in the electron beam. As a result of the radiation exposure, inserting the target material is a dangerous task that requires much care on the part of technicians and exposes them to great risk. 
     Therefore, what is needed is a device and method that can be operated remotely to seal a critical isolated system that is under vacuum or pressure. The vacuum or pressure sealing device should be capable of being operated remotely in order to maintain the isolation of the system and protect personnel from exposure to hazardous materials such as chemicals, cryogenics, and radioactivity. 
     SUMMARY OF THE INVENTION 
     The present invention is a remote vacuum or pressure sealing apparatus and method for sealing a critical isolated system. The remote sealing apparatus includes a fixed threaded sealing surface on an isolated system, a gasket, and an insert consisting of a plug with a protruding sample holder. An insert coupling device, provided for inserting samples within the isolated system, includes a threaded fastener for cooperating with the fixed threaded sealing surface on the isolated system. The insert coupling device includes a locating pin for azimuthal orientation, coupling pins, a toothed coaxial socket wrench, and an insert coupling actuator for actuating the coupling pins. An insertion tool is provided for maintaining the orientation of the insert as well as limiting contact or exposure between the user and the isolated system as the seal is made vacuum or pressure tight. 
     OBJECTS AND ADVANTAGES 
     Several advantages are achieved with the remote vacuum or pressure sealing apparatus and method of the present invention, including:
         (1) The sealing apparatus and method enable remote insertion of samples within an isolated system thereby reducing the potential danger to personnel.   (2) A vacuum or pressure tight seal is providing with the remote sealing apparatus, thereby minimizing the effect of the environment on the isolated system.   (3) An insertion tool portion of the sealing apparatus maintains orientation of the insert and limits exposure of the user to the isolated system.   (4) The sealing method utilizes bearings constructed of a metal dissimilar to that of the isolated system, thereby enabling the pressure on the sealed system to increase as the temperature decreases.   (5) The sealing apparatus maintains a pressure or vacuum tight seal throughout a wide temperature range including 300K-35 mK including temperature cycling within the range.   (6) The sealing apparatus preserves the orientation of the sealing surface with respect to the mating surface, which can be vital for the operation of delicate instrumentation or samples.   (7) The remote aspect of the sealing apparatus maintains the isolation of the system from the user&#39;s environment, safely preserving the user and the system from detrimental effect from each respectively (e.g. radiation, extreme temperature, contamination, etc.).       

     These and other objects and advantages of the present invention will be better understood by reading the following description along with reference to the drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a remote vacuum or pressure sealing apparatus according to the present invention and a portion of an isolated system. 
         FIG. 2  is a sectional view of the remote vacuum or pressure sealing apparatus taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a view of the remote vacuum or pressure sealing apparatus taken along line  3 - 3  of  FIG. 2  showing in detail the rack and pinion arrangement on the inner end of the insertion and coupling tool. 
         FIG. 4  is a sequence of views of the remote vacuum or pressure sealing apparatus of the present invention in various stages as the target stick is removed from the isolated system. 
     
    
    
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 INDEX TO REFERENCE NUMERALS IN DRAWINGS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 20 
                 remote vacuum or pressure sealing apparatus 
               
               
                   
                 22 
                 tubular insertion and coupling tool 
               
               
                   
                 24 
                 tubular insert or target stick 
               
               
                   
                 26 
                 target cup 
               
               
                   
                 28 
                 outer wrench shaft of insertion tool 
               
               
                   
                 30 
                 toothed coaxial socket wrench 
               
               
                   
                 32 
                 teeth 
               
               
                   
                 34 
                 internally threaded fastener 
               
               
                   
                 36 
                 mounted fixed seal 
               
               
                   
                 38 
                 isolated system 
               
               
                   
                 40 
                 inner capture shaft 
               
               
                   
                 42 
                 remote end of inner capture shaft 
               
               
                   
                 44 
                 inner end of inner capture shaft 
               
               
                   
                 46 
                 coupling pin 
               
               
                   
                 48 
                 threaded section 
               
               
                   
                 50 
                 internal threads 
               
               
                   
                 52 
                 gasket 
               
               
                   
                 54 
                 insert including plug and sample holder 
               
               
                   
                 56 
                 bearing race 
               
               
                   
                 58 
                 thrust bearing 
               
               
                   
                 60 
                 first sealing surface 
               
               
                   
                 62 
                 second tapered sealing surface 
               
               
                   
                 64 
                 insert coupling device 
               
               
                   
                 66 
                 insert coupling actuator 
               
               
                   
                 68 
                 bore in target stick 
               
               
                   
                 70 
                 indium seal 
               
               
                   
                 72 
                 rack and pinion arrangement 
               
               
                   
                 74 
                 pinion gear 
               
               
                   
                 76 
                 rack 
               
               
                   
                 78 
                 direction of rotation 
               
               
                   
                 80 
                 directional arrow 
               
               
                   
                 82 
                 outer end of target stick 
               
               
                   
                 84 
                 inner end of target stick 
               
               
                   
                 86 
                 aluminum beam window 
               
               
                   
                 88 
                 locating pin 
               
               
                   
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , the present invention comprises a remote vacuum or pressure sealing system for critical isolated systems. Although the remote sealing device of the present invention has utility for sealing isolated systems under both vacuum and pressure, hereinafter the description of the invention will be in terms of a vacuum sealing system. 
     As shown in  FIG. 1 , a preferred embodiment of the remote sealing system  20  includes an elongated tubular insertion and coupling tool  22  and a tubular target stick  24  with a target cup  26 . The insertion and coupling tool  22  includes an outer wrench shaft  28  and a toothed coaxial socket wrench  30  integral with the lower portion of the outer wrench shaft  28 . The socket wrench  30  includes one or more teeth  32  for engaging an internally threaded fastener  34  that will be threaded upon an externally threaded mounted fixed seal  36  that forms a portion of an isolated system  38 . The isolated system  38  is typically maintained at a vacuum of approximately 1×10 −9  Torr and at temperature of approximately 4 Kelvin. An inner capture shaft  40  having a remote end  42  and an inner end  44  extends through the outer wrench shaft  28  of the tubular insertion and coupling tool  22 . Coupling pins  46  are provided at the inner end  44  of the inner capture shaft  40 . Note that the elongated tubular insertion and coupling tool  22  can be constructed of various lengths to provide adequate protection to a user. 
     As shown in  FIG. 2 , the top end of the mounted fixed seal  36  includes a threaded section  48  thereon. Threaded fastener  34  includes internal threads  50  for engaging the threaded section  48  of the mounted fixed seal  36 . Surrounding target stick  24  there is provided a gasket  52 , an insert  54 , bearing races  56 , and a titanium thrust bearing  58 . A first sealing surface  60  is provided above and a second tapered sealing surface  62  is provided below the gasket  52 . The tubular insertion and coupling tool  22  includes an insert coupling device  64  with a locating pin  88  for azimuthal orientation of the target stick during seal commissioning and an insert coupling actuator  66 . Bores  68  are provided in the top portion of the target stick  24  and an indium seal  70  is provided between the lower surface of the mounted fixed seal  36  and the isolated system  38 . 
     The remote sealing system  20  provides an apparatus and method for sealing a critical isolated system. As shown in  FIG. 2 , the tubular insertion and coupling tool  22  can be used to couple to the target stick  24  and insert or remove the target stick  24  from the isolated system  38 . The insertion and coupling tool  22  is used to maintain orientation of the target stick  24  as well as limiting contact and exposure between the user and intended isolated system  38  as the seal is made vacuum tight, thus minimizing the effect of the environment on the isolated system. The sealing method of the present invention employs dissimilar metals, specifically bearing races  56  and a thrust bearing  58  that are constructed of a metal with a lower thermal contraction rate than that of the metal portions of the isolated system  38 . Typically, the metal portions of the isolated system  38  are constructed of stainless steel. Therefore the thrust bearing  58  and bearing races  56  are preferably constructed of a metal that includes a lower thermal contraction rate than the stainless steel. In the preferred embodiment, the thrust bearing  58  and bearing races  56  are constructed of titanium. 
     Referring to  FIG. 3 , the inner end  44  of the capture shaft  40  includes a rack and pinion arrangement  72  for coupling and uncoupling the insertion tool  22  to the target stick (not shown). A pinion gear  74  is provided on the end of capture shaft  40  and a rack  76  is provided on the inner sides of each coupling pin  46 . Rotation of pinion gear  74  in the direction of rotation, shown by directional arrow  78 , moves each coupling pin  46  in the direction of arrow  80 . Thus, rotation of pinion gear  74  via the insert coupling actuator  66 , in a first direction drives the coupling pins  46  outward with respect to the capture shaft  40  thereby causing coupling pins  46  to extend through bores  68  in target stick (not shown) and thereby couple the insertion tool  22  to the target stick. Rotation of insert coupling actuator  66  in the opposite direction will cause the coupling pins  46  to retract through bores  68  and thereby release the target stick. 
     The remote vacuum or pressure sealing apparatus  20  provides a method of removing or inserting a target material into an isolated or hazardous system remotely, thereby providing protection to the operator. Operation of the sealing apparatus is described herein for removal of a target from an isolated system. With reference to  FIG. 2 , for removing a target the present invention is operated by retracting the coupling pins  46  and advancing the tubular insertion and coupling tool  22  until the inner end  44  is inserted within the outer end  82  of the target stick  24 . The relative orientation between coupling tool  22  and target stick  24  is determined by the azimuthal locating pin  88 . Insert coupling actuator  66  is then turned to cause rotation of pinion gear  74  thereby driving the coupling pins  46  to the extended position through the bores  68  in the target stick  24  and thereby locking the coupling tool  22  to the target stick  24 . The toothed coaxial socket wrench  30  then descends over and envelops the capture shaft  40  until the teeth  32  of the tooth coaxial socket wrench  30  and the internally threaded fastener  34  engage. The outer wrench shaft  28  is then rotated counterclockwise to loosen the internally threaded fastener  34  from the mounted fixed seal  36  thus eliminating the force on the gasket  52  and breaking the seal. The inner capture shaft  40  is then slowly retracted with the target stick  24  attached and removed from the isolated system  38   
     The various steps described above in the operation of the remote vacuum or pressure sealing apparatus  20  to remove a target from an isolated system are shown in a series of drawings, labeled a through f, in  FIG. 4 . From left to right in the figure, the steps include a) the tubular insertion and coupling tool  22  with coupling pins  46  is placed in axial alignment with the target stick  24 ; b) the pins of the coupling tool  22  are extended through bores  68  in target stick  24  to lock the coupling tool  22  to the target stick  24 ; c) toothed coaxial socket wrench  30  is advanced until the teeth  32  engage the internally threaded fastener  34 , at this point internally threaded fastener  34  is interlocked with the mounted fixed seal  36  and the titanium thrust bearing  58  is maintaining a vacuum tight seal as a result of the lesser thermal contraction rate of the titanium as compared to the stainless steel threaded fastener  34 ; d) outer wrench shaft  28  is turned counterclockwise to loosen the internally threaded fastener  34 ; e) the inner capture shaft  40  is retracted with the target stick  24 ; and f) the target stick  24  is pulled out of the mounted fixed seal  36  and the isolated system  38 . Insertion of a target stick  24  into the isolated system  38  is essentially reversing the above steps a-f with a new kapton gasket placed over the target stick  24 . 
     With reference to  FIG. 2 , since the invention takes advantage of the properties of dissimilar metals to create a vacuum-tight seal, the choice of materials is critical to the practice of the present invention. The sealing apparatus has been tested on isolated systems that in a high radiation environment and are maintained at a vacuum of approximately 1×10 −9  Torr and at temperature ranging from 0.035 up to 300 Kelvin. The major portions of the remote vacuum or pressure sealing apparatus  20  that form the seal, including the internally threaded fastener  34 , mounted fixed seal  36 , and the target stick  24 , are constructed of stainless steel. The thrust bearing  58 , and the bearing races  56  if desired, are constructed of a metal that has a lower thermal contraction rate than stainless steel. Preferably the bearing races  56  and thrust bearing  58  are constructed of titanium. The gasket is preferably constructed of crushable materials such as polymers or films including biaxially-oriented polyethylene terephthalate and polyimide, or metals such as copper, aluminum, or indium. Most preferably, the gasket is formed of polyimide. Biaxially-oriented polyethylene terephthalate and polyimide films include trade names MYLAR® and KAPTON® respectively and are available from DuPont Company, Wilimington, Del. Thus, after the target stick  24  has been inserted into the isolated system  38  and the internally threaded fastener  34  torqued to the proper force onto the mounted fixed seal  36  to form the seal, the isolated system is allowed to return to the steady state conditions of approximately 1×10 −9  Torr and 4 Kelvin. As the internally threaded fastener  34  approaches the temperature of the isolated system  38 , the titanium thrust bearing  58  and the bearing races  56  contract at a lesser rate than the surrounding stainless steel portions of the seal. Thus, as the system cools, the titanium thrust bearing  58  and bearing races  56  exert increasing pressure on the seal thereby applying more pressure on the gasket  52  at both the first sealing surface  60  and second sealing surface  62 . The taper of the second sealing surface  62  incorporated into the mounted fixed seal  36  adds additional force due to the geometry. An inward radial force occurs as the first sealing surface  60  on the insert plug  54  approaches equilibrium. If the thrust bearing  58  and bearing races  56  were constructed of the same material as the internally threaded fastener  34  and insert  54 , or of a material with a higher thermal contraction rate than the stainless steel, the bearing  58  and bearing races  56  would exert less force as the isolated system came to equilibrium, and this would cause an undesirable loss of vacuum. 
     Although the remote vacuum or pressure sealing apparatus  20  is shown in a vertical orientation throughout the specification and figures herein, it should be emphasized that the sealing apparatus can be used in any orientation. The remote vacuum or pressure sealing apparatus  20  of the present invention has been used extensively in a substantially horizontal orientation in the beam line of a particle accelerator for insertion of targets and forming a vacuum-tight seal therein. 
     The sealing method of the present invention therefore employs dissimilar metals, in this example titanium bearing races  56  and a titanium thrust bearing  58  to enhance the force on a gasket  52  that is mechanically crushed between two sealing surfaces  60  and  62 . The sealing method takes advantage of the differential thermal contraction rates of various components and the geometry of sealing surfaces to compliment the sealing force provided by the threaded coupling of internally threaded fastener  34  to the mounted fixed seal  36 . 
     Additionally, the geometry of the sealing surfaces  60  and  62  work in conjunction with the dissimilar metal providing further assurance of seal integrity throughout the temperature range so long as the temperature of the insert (including sample holder  54 , threaded fastener  34 , titanium bearing races  56 , and titanium thrust bearing  58 ) is greater than the temperature of the fixed threaded sealing surface  48  when securing the threaded coupling. In an effort to minimize torque required to tighten the threaded coupling, the titanium bearing  58  is a thrust bearing thereby reducing frictional drag forces and seizing due to foreign contamination. The thrust bearing  58  makes the friction of the engaged threads  48  and  50  the dominating frictional force minimizing the torque and reducing the stress on the insertion tool  22 . 
     With reference to  FIG. 1 , the inner end  84  of target stick  24  includes target cup  26  which holds target particles for use in scattering experiments in the beam line of a particle accelerator. The target particles are typically doped butanol beads which provide a polarized material for scattering experiments. A thin aluminum beam window  86 , with a thickness of between 0.007 and 0.010 inch is provided at the end of the target stick. 
     Although the description above contains many specific descriptions, materials, and dimensions, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.