Patent Publication Number: US-6212854-B1

Title: Apparatus for charging canisters with a high pressure gas

Description:
This is a continuation of patent application Ser. No. 08/677,948 filed on Jul. 10, 1996, now U.S. Pat. No. 5,829,223. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to the manufacture of components for inflatable restraining systems used in automotive vehicles, and more particularly to an apparatus for charging metallic canisters used in such systems with a gas under high pressures and sealing such canisters while maintaining them under pressure. 
     In the prior art, there has been developed an apparatus for pressurizing metallic canisters used in inflatable restraining systems for automotive vehicles by injecting a gas under pressure through a filler opening provided in the canister and then sealing such filler opening while continuing to supply pressurized gas to the canister. Generally, such apparatus is provided with a member engageable in sealing relation with a canister being charged, having a guide passageway communicable with the filler opening of the canister. Such member can be either stationary with means for displacing the canister into sealing engagement with the member or displaceable with means for displacing the member into sealing engagement with the canister. In either of such arrangements, with the member disposed in sealing engagement with the canister and the guide passageway of the member communicating with the filler opening in the canister, means are provided for injecting an inert gas under pressure through the guide passageway in the sealing member and the filler opening in the canister to pressurize the canister, delivering a welding ball through the guide passageway of the sealing member so that it deposits on the canister across the filler opening therein and for extending a welding rod through the guide passageway in the sealing member to positively engage and fuse the welding ball and close the filler opening while continuing to maintain the canister under pressure. An example of such type of apparatus is described and claimed in U.S. Pat. No. 5,352,860. 
     Canisters intended to be pressurized by such type of apparatus often vary in configuration, wall thickness, filler opening size and charging pressure requirement. Accordingly, for such an apparatus to be effective and productive, it must be capable of pressurizing such canisters at pressures in the range of 3,500 to 10,500 psi, positively maintaining a seal between the sealing member and the canister to accommodate such high pressures, reliably delivering welding balls of different sizes to accommodate canister filler openings of different sizes, and effectively preventing leakage of gas, particularly through the welding ball feeding mechanism. 
     It thus has been found to be desirable to provide an apparatus of the type described which is capable of not only providing an effective seal between the sealing member and the canister and pressurizing the canister while maintaining such seal but of reliably feeding welding balls of different sizes to accommodate canisters of different filler hole sizes. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides an apparatus comprising a sealing member having a passageway therethrough displaceable between a first position out of engagement with a canister to be pressurized and a second position engageable in sealing engagement with the canister with the guide passageway therein communicating with the filler opening in the canister, means for conveying a gas under pressure to the guide passageway of the sealing member when the sealing member is in sealing engagement with the canister, a rotary valve for feeding a welding ball through the guide passageway to cause the ball to deposit on the canister across the filler opening therein, while the sealing member is maintained in sealing engagement with the canister and the canister is under pressure, and a welding rod disposed in the guide passageway of the sealing member and displaceable into positive mechanical and electrical contact with a welding ball deposited on a canister for fusing the welding ball and welding closed the filler opening in the canister while continuing to maintain the sealing member in sealing engagement with the canister and the canister under pressure. 
     Preferably, the apparatus includes a gate displaceable between a first position in a nonobstructing relation to a welding ball conveying means and a second position in obstructing relation therewith, such gate is mechanically connected to the sealing member so that the gate is in a nonobstructing relation with a welding ball conveying means when the sealing member is disposed in its retracted position out of sealing engagement with a canister and in obstructing relation with the welding ball conveying means when the sealing member is disposed in its extended position in sealing engagement with a canister, and the rotary valve is operable to feed a welding ball into the welding ball conveying means when the gate is in obstructing relation with the welding ball conveying means for holding a welding ball in abeyance to be delivered to the guide passageway of the sealing member during the next operating cycle of the apparatus. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a system for loading an empty canister on a retaining fixture in a selected orientation, forming a gas filling opening in the canister, charging the canister with a gas under pressure through the formed opening and closing and sealing the opening, utilizing an apparatus embodying the present invention. 
     FIG. 2 is an enlarged, vertical cross-sectional view of the apparatus utilized in the system shown in FIG. 2 for sequentially filling the canister with a gas under pressure through a gas filling opening in the canister and then sealing such opening, embodying the present invention. 
     FIG. 3 is a schematic-diagrammatic view of the apparatus shown in FIG.  2  and the fluid supply system therefor. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
     Referring to the drawings, there is illustrated a system for charging a metallic canister with an inert gas under pressure and then sealing the canister including an apparatus embodying the present invention. The system consists of an apparatus  10  including a canister loading station  11 , a filler hole forming station  12 , a preweighing station  13 , a gas charging and sealing station  14 , a post weighing station  15  and an unloading station  16  and a gas supply system  17 . The apparatus is provided with a main frame  18  on which there is mounted a conveyor  19  for advancing a canister supporting pallet  20  sequentially from canister loading station  11  through unloading station  16 . Each of such pallets includes a canister retaining fixture adapted to position the canister in a predetermined orientation to allow for the formation of a filler opening in the canister at the hole forming station and subsequent charging of a gas under pressure into the canister through the opening therein and the sealing of such opening at the gas charging and sealing station. 
     Mounted on the main frame at station  12  is a hole piercing assembly. Such assembly is positioned on the main frame relative to the conveyor so that when a pallet carrying a canister disposed in a selected orientation is positioned at station  12 , the piercing tool of the assembly will be vertically aligned with the portion of a canister to be punctured. Mounted on the main frame at station  13  is a transfer mechanism  21  which is adapted to laterally displace a pallet  20  positioned at station  13 , weigh the empty, pierced canister and transfer it laterally back onto the conveyor for advancement to station  14 . A gas charging and sealing apparatus which embodies the present invention is mounted on the main frame at station  14  which functions to charge a canister supported on a pallet positioned at station  14  with a gas under pressure, and then seal the gas filling hole in the canister in a manner to be described. 
     Disposed between stations  14  and  15  or at station  15  is a means for detecting a defective canister. Also mounted at station  15  is a mechanism for post-weighing a filled and sealed canister positioned at station  15 , and a defective canister processing assembly. Upon detection of a canister with a defective filling hole closure or an underweight or overweight canister positioned at station  15 , the defective canister processing assembly will be operated to drill a relief hole in the canister and allow the release of gas from the canister. The pallet supporting canisters at station  15  are then transferred laterally by a mechanism  22  from where they are advanced to station  16  for unloading. 
     Preferably, conveyor  19  is an endless conveyor on which successive pallets  20  are spaced apart the distance between successive stations on the apparatus. Canisters loaded onto fixtures supported on pallets at the loading station are incrementally advanced by the conveyor sequentially to station  12  where the gas filling hole is formed, station  13  where the canister is preweighed, station  14  where the canister is charged with a gas under pressure and the gas filling hole in the canister is welded closed, station  15  where the canister is post-weighed and defective canisters are drilled to release the gas therein and station  16  where the canister is removed. 
     Referring to FIG. 2, there is shown an apparatus  30  which is mounted on the main frame of the apparatus shown in FIG. 1 for charging a canister positioned at station  14  with a gas under pressure through a filler opening in the canister formed at station  12 , and then sealing such filler opening to provide a closed, pressurized canister. The assembly generally includes a housing  31 , a sealing member  32 , a welding ball feed mechanism  33 , a welding ball transfer mechanism  34  and a welding rod assembly  35 . The housing is formed of a number of annular steel plates bolted together to provide a longitudinal bore  36  therethrough having an enlarged section  37  provided with a cylindrical side wall and opposed, annular end walls. The housing is adapted to be seated on an annular member  38  mounted on a crosspiece member  39  of main frame  18 . 
     Sealing member  32  is disposed in longitudinal bore  36  and is adapted to be displaced therein between a retracted position as shown in FIG.  2  and an extended position. The member is substantially tubular in configuration, providing an axially disposed guide passageway  40 . It further is provided with an annular section  41  received within enlarged section  37  of opening  36 . The sealing member with annular section  41  cooperates with the cylindrical side wall and annular end walls of enlarged section  37  to provide a pair of variable volume chambers  42  and  43 . Communicating with chamber  42  is a fluid passageway  44 . Similarly provided in housing  31  is a fluid passageway  45  which communicates with chamber  43 . Suitable seals are provided between displaceable sealing member  32  and housing  31 . It will be appreciated that by supplying fluid under pressure to one of chambers  42  and  43  while venting the other, annular section  41  will function as a piston to displace the sealing member between the retracted and extended positions in the conventional manner. 
     Sealing member  32  further is provided with a transversely disposed access opening  46  at a point intermediate annular section  41  and an end portion thereof. Access opening  46  communicates with guide passageway  40 , and is adapted to be displaced between a first positioned as shown in FIG. 2 when the sealing member is in the retracted position, and a second position communicating with a ball transfer passageway  47  and a gas supply passageway  48  in the housing when the sealing member is in the extended position. The outer end of sealing member  32  is provided with an internally threaded opening into which a tip section  49  is threaded. The tip section is provided with a longitudinal passageway aligned with guide passageway  40 , which is provided with an electrical insulating lining  50 . Guide passageway  40  of the sealing member similarly is provided with an electrical insulating lining  51 . 
     Preferably, access opening  46  is located at a point as close as possible to the dispensing end of the sealing member with communicable passageways  47  and  48  similarly being located at a lower end of the housing to minimize the length of path of gas injected through apparatus  30 . Such opening, however, could be located at any suitable point along the length of the sealing member. Furthermore, although only a single access opening is provided in the embodiment shown in the drawings communicable with both passageways  47  and  48 , it is contemplated within the scope of the invention to provide two separate access openings, one communicating with passageway  40  and communicable with passageway  47  and the other communicating with passageway  40  and communicable with passageway  48 , when the sealing member is in the extended position. Furthermore, such two access openings can be longitudinally spaced along the length of the sealing member. 
     Mounted on a lower end of tip section  49  and adapted to engage a portion of a canister disposed about the periphery of the filler opening thereof, when the sealing member is in the extended position, is an electrical grounding assembly  52 . The assembly includes an annular metallic supporting member  52   a  seated on an annular member  53  rigidly secured to and displaceable with tip section  49 , an annular insulator spacer  54  mounted on the underside of member  52   a,  an annular member  55  mounted on the spacer, and an annular, canister engaging member  56 , secured together by a set of bolts  57 . Annular member  55  is provided with a portion having an inner diameter greater than the outer diameter of annular member  53  to permit longitudinal displacement of member  53  relative to member  55 . Annular member  52   a  is urged into seating engagement with member  53  by means of a set of circumferentially spaced springs  58  interposed between an annular member  59  rigidly secured to and displaceable with the sealing member, and annular member  52   a . It will be appreciated that when the sealing member is displaced to its extended position with the end section thereof engaging a canister, canister engaging member  56  will engage the canister about an outer perimeter of the filler opening therein in advance of tip section  49  engaging the canister about an inner perimeter of the filler opening, to provide a suitable mechanical and electrical contact with the canister. Such engagement is facilitated by springs  58  which function to urge and maintain engaging member  56  in positive mechanical and electrical contact with the canister. When annular engaging member  56  is in engagement with the canister, displacement of member  53  relative to member  55  is permitted by the spacing of member  53  and the inwardly extending portion of member  55 , as the tip of the sealing member engages the canister about the periphery of the filler hole in sealing engagement therewith. 
     The function of welding ball feed mechanism  33  is to feed a welding ball to the ball transfer mechanism for injection through access passageway  41  and guide passageway  40  in the sealing member, causing it to drop and be deposited on a canister across the filler opening therein. The mechanism operates to meter a single ball at a time through passageways  60  and  61  in the housing to passageway  47  where it is transferred into the guide passageway of the sealing member through access passageway  46  in the sealing member by transfer mechanism  34 . The feed mechanism includes a rotary actuator  62  having an end bracket  63  rigidly secured to housing  31  and a shaft  64  extending into a recess  65  in the housing having a cylindrical side wall. Mounted on the end of shaft  64  and disposed within recess  65  is an annular feed valve  66  having a substantially radially disposed pocket in the outer cylindrical surface thereof relative to the axis of shaft  64 . In a first position as shown in FIG. 2, the ball receiving opening in feed valve  66  is adapted to register with and receive a single welding ball from a feed chute  67 . The chute is connected to a continuous supply of welding balls which are guided through a flexible tube connected to the feed chute. In a second position angularly displaced 180° from the first position, the ball receiving opening is adapted to register with an inlet of passageway  60 . It will be appreciated that with rotary feed valve  66  being in the position as shown in FIG. 2, a ball in the feed chute will be caused to be received in the ball receiving pocket of rotary feed valve  66  and upon rotating shaft  64  180°, such ball will be fed to passageway  60  from where it will be caused, if unobstructed, to be delivered to passageway  47 . 
     The passage of a ball from passageway  60  to passageway  47  is controlled by a sliding gate  68  displaceable in passageway  61  between a retracted, nonobstructing position as shown in FIG. 2, and an extended, obstructing position, blocking the passage of a ball from passageway  60  into passageway  61 . The displacement of the sliding gate between its retracted and extended positions is actuated by and thereby coordinated with the displacement of the sealing member by means of a floating connection between the outer end portions of such members. The connection is provided by an arm member  69  which is rigidly secured to the outer end of the sealing member by a threaded member  70  and connected to the sliding gate by a bolt  71  in a manner whereby the gate will be lifted when the sealing member is retracted and allowed to drop when the sealing member is extended. With such a connection, it will be appreciated that when the sealing member is in its retracted position as shown in FIG. 2, sliding gate  68  similarly will be in a retracted position with the opening between passageways  60  and  61  being unobstructed to permit a welding ball to pass therethrough into passageway  47 . When the sealing member is in the extended position, the gate will be permitted to drop and close passageway  60 . 
     When the sliding gate is in its extended position, a suitable seal is provided between the sliding gate and housing  31 , at a point between passageways  60  and  47 , to prevent a loss of gas under pressure injected through passageway  48 . 
     Ball transfer mechanism  34  includes a pneumatic cylinder assembly  80  mounted on housing  31 , having a ball transfer slide  81  received within ball transfer passageway  47  and displaceable therein between a retracted position as shown in FIG.  2  and an extended position. Ball transfer slide  81  includes a slot  82  therein which is adapted to register with passageway  61  when the slide is in the retracted position. The slide is adapted to displace to its extended position only upon the displacement of the sealing member into its extended position with access opening  46  registered with passageway  47  to permit the transfer slide to be received within access opening  46  of the sealing member and permit slot  82  to be aligned with guide passageway  40  in the sealing member to further permit a welding ball to drop into the guide passageway of the sealing member. 
     A suitable seal also is provided between transfer slide  81  and housing  31  at a point between the juncture of passageways  61  and  47  and an outer end of passageway  47 , to further prevent the loss of gas under pressure injected through passageway  48 . 
     Welding rod assembly  35  includes a welding rod  90  extending through guide passageway  40  and being displaceable between a retracted position as shown in FIG.  2  and an extended position engaging a welding ball deposited on a canister, across the filler opening therein. The upper end of the welding rod is secured to a support member  91  which is operatively connected to a pneumatic cylinder assembly for displacing the welding rod between its retracted and extended positions. The welding rod further is electrically connected to a secondary lead of a welding transformer with the electrical grounding assembly  52  connected to the other secondary lead of the transformer so that upon the sealing member being disposed in its extended position with canister engaging member  56  in positive mechanical and electrical engagement with a canister, the welding rod being in its extended position in positive mechanical and electrical contact with a welding ball deposited on the canister across the filler opening thereof, and alternating current being supplied, the welding ball will be caused to fuse and thus flow and seal the filler opening closed. 
     A suitable seal also is provided between welding rod  90  and sealing member  32 , again to prevent a loss of gas under pressure injected through passageway  48  when the sealing member is in the extended position. 
     Gas supply system  17  functions to provide gas under pressure to normally urge sealing member  32  in its retracted position out of engagement with a canister to be pressurized, advance the sealing member into its extended position in sealing engagement with a canister, with the guide passageway therein in communication with the filler opening in the canister and transverse access opening  46  thereof in communication with ball transfer passageway  47  and fluid passageway  48 , and further to supply a gas under pressure through passageways  48 ,  46  and  40  to pressurize the canister through the filler opening therein when the sealing member is in its extended position providing a fluid tight seal between the sealing member and the canister. The system includes a main fluid supply line  100  provided with a pair of branch lines  101  and  102 . Main fluid line  100  is connected to a source of fluid under pressure and includes an accumulator  103  and a main shut-off valve  104 . Branch line  101  is connected to fluid passageway  48  and includes a pressure regulator  105 , a relief valve  106  and a pneumatically actuated valve  107 . Connected to branch line  101  between valve  107  and fluid passageway  48  is a branch line  108  provided with a pneumatically actuated valve  109 . Valve  107  is normally in the closed position and valve  109  normally is in the open position. Such valves are operated by an electrically operated solenoid valves  110  and  110   a.    
     Branch line  102  is connected to fluid passageway  44  of apparatus  30  and is provided with a pressure regulator  111  and a pneumatically actuated valve  112 . Interconnecting fluid line  102  at a point between pressure regulator  111  and valve  112  is a branch line  113  connected to fluid passageway  45  of apparatus  30 . Such branch line includes a pressure regulator  114  and a pneumatically actuated valve  115 . Valve  112  is normally positioned to vent fluid passageway  44 , and valve  115  is normally in the closed position to provide fluid under pressure to fluid passageway  45  of apparatus  30 . Valves  112  and  115  are operated by electrically operated solenoid valves  116  and  116   a.    
     A conventional controller is used to operate solenoid valves  110 ,  110   a,    116  and  116   a  and solenoid valves controlling the operations of rotary actuator  62 , cylinder assembly  80  and the cylinder assembly for displacing the welding rod assembly, and to energize the welding rod circuit, in a proper sequence to charge and seal a canister in a manner as hereinafter described. 
     OPERATION 
     With a main line pressure of 10,000 psi, pressure regulator  105  set at 4,500 psi, pressure regulator  111  set at 5,000 psi, pressure regulator  114  set at 500 psi and the various valves being in the positions as shown in FIG. 3, gas under a pressure of 500 psi will be supplied to fluid passageway  45  of assembly  30  to cause the sealing member to be urged into its retracted position as shown in FIGS. 2 and 3. Upon a canister being positioned at station  14  with its filler opening aligned with the guide passageway of sealing member  32 , the controller will operate solenoid valves  116  and  116   a  to shift valves  115  and  112  to vent fluid passageway  45  and supply a gas under 5,000 psi to fluid passageway  44  of apparatus  30 . Under such conditions, sealing member  32  will be displaced from its retracted to its extended position so that electrical ground assembly  52  will engage the canister about an outer perimeter of the filler hole therein to provide a positive mechanical and electrical contact, and sequentially tip section  49  of the sealing member will engage the canister about an inner perimeter of the filler hole therein in sealing engagement, with guide passageway  40  in the sealing member communicating with the interior of the canister through the filler opening. 
     The force applied on the sealing member in contact with the canister would be sufficient to provide an effective seal yet not allow the canister to collapse, unduly deform or become unduly stressed. Upon the seal between the sealing member and canister having thus been formed, the controller next functions to operate valves  110  and  110   a  to open valve  107  and close valve  109 . Under such condition, gas under a pressure of 4,500 psi will be supplied to fluid passageway  48  to pressurize the canister. Valve  107  is then closed. While maintaining such pressure, transfer mechanism  34  is operated to displace transfer slide  81  from its retracted position as shown in FIG. 2 to its extended position within access opening  46  of the sealing member, allowing a welding ball having been deposited in slot  82  of the transfer slide to drop through the lower end of guide passageway  40  and be deposited on the canister across the filler opening therein, in alignment with welding rod  90 . The transfer slide is then returned to its “home” position as shown in FIG.  2 . 
     With the welding ball thus positioned and the filling pressure maintained, the controller next functions to sequentially displace the welding rod from the retracted position as shown in FIG. 2 to an extended position in positive mechanical and electrical contact with the welding ball seated across the filler opening in the canister, and energize the welding circuit, causing the welding ball to fuse and close the filler opening in the pressurized canister. 
     While the sealing member is in the extended position, sliding gate  68  similarly will be in an extended position blocking communication of ball passageway  60  with ball passageway  61 . Under such circumstances, the controller will function to operate rotary actuator  62  causing the shaft to rotate 180° to transfer a ball in the recess of annular feed valve  66  to ball passageway  60  where it rolls down against extended sliding gate  68 , postured to fall into and through ball passageway  61  and be received in slot  82  of the transfer slide when the transfer slide is in its retracted position and the sliding gate is next displaced to its retracted position. 
     Upon the passage of a predetermined interval of time to allow the fused ball to solidify and form a closure in the filler opening of the canister, the controller functions to operate valve  110   a  to open valve  109  to vent passageway  48 . Once the charging assembly has been evacuated, the controller functions to again close valve  109  and the pressure in the charging assembly is sensed to determine whether there is any leakage through the fused seal. The controller then functions to shift valve  112  to vent fluid passageway  44  and close valve  115  to again pressurize fluid passageway  45  and correspondingly cause sealing member  32  to retract to the position as shown in FIGS. 2 and 3. The gas charging and sealing assembly is then positioned to begin a new cycle as the next canister is advanced into position. 
     Under circumstances where it is desired first to test the structural integrity of the canister prior to pressurizing it to its operating pressure, the same procedure may be followed except for setting pressure regulator  105  at a pressure greater than the desired fill pressure, in the order of perhaps 8,500 psi, to initially pressurize the canister at such elevated pressure, and for then operating valves  110  and  110   a  to sequentially close valve  107  and bleed gas from the canister by opening valve  109  until the pressure in the canister is reduced to the operating pressure of 4,500 psi. To control such pressure reduction, a transducer  117  is provided to sense the pressure in the canister and cause the controller to close valve  109  when the desired operating pressure in the canister has been reached. 
     In addition to branch line  113  being used to cause a retraction of the sealing member, the setting in pressure regulator  114  may be set at different settings and valve  115  may be opened to supply gas under pressure to fluid passageway  14  while gas under pressure is supplied to fluid passageway  44  to provide a pressure differential across the sealing member. Under such circumstances, the force applied on the sealing member may be varied to correspondingly vary the force applied in forming the seal. With such capability, canisters formed of different materials or possibly having different wall thicknesses may be accommodated without causing structural damage to such canisters in forming the seal as described. 
     The settings of the pressure regulators may be set at any desired settings depending on the required filling pressures or the required testing and filling pressures. Preferably, the sealing pressure determined by pressure regulator  111  would be in the range of 2,000 to 5,000 psi and the testing and fill pressures determined by pressure regulator  105  would be in the range of 3,500 to 10,500 psi. The retract pressure determined by pressure regulator  114  can be set at any lower pressure such as 500 psi, sufficient to provide a force to retract the sealing member except when it may be desired to provide a differential pressure to more accurately control the sealing force of the sealing member as previously described. 
     To provide even greater flexibility in accommodating canisters having different size filler openings, the width or diameter and depth of the ball receiving pocket in annular feed valve  66  and the width of ball receiving slot  82  in the transfer slide are made sufficiently large to accommodate welding balls of different sizes. Alternatively, different feed valves and transfer slides accommodating different size welding balls may be used. 
     By the use of independent sources of pressure for effecting the seal between the sealing member and the canister, and for pressurizing the canister, an effective and consistent seal is provided during the canister pressurization operation and particularly during the application of variable pressures as during the testing and filling procedure as previously described. In addition, the use of such separate sources of pressure permits the application of a differential pressure on the sealing member providing a greater flexibility in operation. 
     From the foregoing detailed description, it will be evident that there are a number of changes, adaptations and modifications of the present invention which come within the province of those having ordinary skill in the art to which the aforementioned invention pertains. However, it is intended that all such variations not departing from the spirit of the invention be considered as within the scope thereof as limited solely by the appended claims.