Abstract:
The present invention is for a method of testing a seal on a collapsible tube dispensing orifice during the manufacturing process. Air pressure is applied on one side of the seal, and the pressure is monitored on the other side of the seal, for any increase in pressure which would indicate a leak in the seal.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     (1) Field of the Invention This invention relates generally to a collapsible tube used to contain and dispense fluids, and particularly to a seal on the dispensing orifice of such a tube.  
         [0002]     (2) The Prior Art Collapsible tubes are packages in tube form having a dispensing orifice at one end of a deformable tube. The tube is deformed and collapsed by squeezing so that the contents are forced out of the orifice. Such tubes are used to contain toothpaste, pharmaceuticals, cosmetics, personal care products, artists&#39; pigments, adhesives, sealants and caulking materials, greases and lubricants, foods and condiments, and many other products. A collapsible tube generally has a screw closure cap.  
         [0003]     Such tubes are made of metal, such as lead, tin and aluminum, or of plastic or laminate materials.  
         [0004]     Collapsible tubes often have a seal across the dispensing orifice of the tube, particularly when used for medicinal products. The seal prevents the tube contents from leaking out prior to use. Also, the seal prevents any atmospheric contact with the tube contents, since the tube is sealed in an air-tight manner.  
         [0005]     In use, the seal is pierced by, for instance, a point formed in the tube screw cap.  
         [0006]     A method of forming a seal on a collapsible tube is shown in U.S. Pat. No. 4,938,818, incorporated herein by reference.  
         [0007]     This invention is specifically directed to a method of testing such a seal for leaks.  
       SUMMARY OF THE PRESENT INVENTION  
       [0008]     The present invention as seen in the drawings, provides a method of testing the seal on a collapsible tube during the manufacturing process, wherein tube components that include a head  21  with a dispensing orifice, a tube wall  22  that is secured to the head  21 , a seal  35  that is applied over the dispensing orifice, and a screw closure cap  37 , are all, at stations, assembled into the completed tube  118 . The tube wall  22  is left open at the bottom for subsequent filling and closing.  
         [0009]     In the present invention, in testing for a seal  35  that leaks, air under pressure is applied to one side of the seal  35 , at a station  201  in the manufacturing process of the tube, and any increase in pressure on the opposite side of the seal  35  is noted.  
         [0010]     Such pressure increase indicates a seal  35  that is defective and leaks.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a schematic side elevational view of successive stations in the manufacturing process that includes a station  201  that tests a seal for leaks, in accordance with the present invention. The station that tests for leaks is installed between stations in the manufacture of the tube. Such stations in the manufacture of the tube are shown in  FIG. 7  of the &#39;818 patent.  
         [0012]      FIG. 2  is an enlarged view of the testing station of the invention shown at  201  in  FIG. 1 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0000]     The Prior Art In the &#39;818 patent referred to above, a seal disc is bonded to the dispensing orifice on the head of a collapsible tube, and the head of the tube is bonded to a preformed tube wall, by radio frequency.  
         [0013]     After applying a closure cap to the threaded neck of the head, the open bottomed tube is ready to be shipped to a purchaser for filling through the tube open bottom, after which the tube is closed at the bottom.  
         [0000]     The Improvement  
         [0014]     In present invention, as seen in  FIG. 1 , a seal  35  bonded to the dispensing orifice of a head  21  of collapsible tube  118  is tested for leaks at a testing station  201 , which is positioned between stations of a prior art tube manufacturing line, as disclosed in the &#39;818 patent. The tube is formed at station  200  (designated station  90  in the &#39;818 patent) in accordance with the disclosure of the &#39;818 patent, where a movable, reciprocating, power-driven cap  210  bonds the seal  35  to the dispensing orifice of head  21 , and tube wall  22  to the head  21 , with radio frequency waves.  
         [0015]     Cap  210  reciprocates horizontally, and tube  118 , on mandrel  203  is indexed to station  201 , where the testing for leaks occurs. The vacuum that has been applied at station  200 , in accordance with the prior art teaching of the &#39;818 patent, is turned off before indexing to station  201 . At station  201 , stopper  211  is moved upward into cavity  207  of mandrel  203  by hydraulic plunger  212 , the shaft of which reciprocates vertically as shown at  213 . Flexible hose  215  is connected to a regulated and valve activated compressed air pump  216  which provides air under pressure at, for instance, 40 pounds per square inch, to the interior of collapsible tube  118 . The air pressure is such that the seal  35  can retain the pressure without bursting.  
         [0016]     The stopper  211  and cavity  207  in mandrel  203  each desirably have a soft surface so they can readily form a tight force fit during the testing.  
         [0017]     Simultaneously with movement of stopper  211  into position at the bottom of the tube  118  at station  201 , a top cover  220 , as seen at station  201  in  FIGS. 1 and 2  of the present drawings, moves downward at the end of vertically reciprocating shaft  221 , to cover seal  35 , and to make contact with head  21 . Cover  220  forms an airtight joint with head  21 .  
         [0018]     A pressure sensor  222  is supported from cover  220 , with conduit  223  connected to the interior of cover  220 .  
         [0019]     In operation, during the manufacturing of the tubes  118 , the tubes  118  to be tested are intermittently moved into station  201 , where cover  220  is moved into contact with head  21 , forming an airtight compartment over the seal  35  and head  21 . Simultaneously, at station  201 , stopper  211  is inserted upwardly into cavity  207  and air at a given pressure enters tube neck  30 . If the seal  35  is tight with no leaks, air under pressure is maintained inside the tube  118 , and no air leaks through the seal.  
         [0020]     In the event of a leak in the seal  35 , air escapes up into cover  220 , and the pressure within cover  220  builds up and is detected by the pressure sensor  222 . The tube  118  with the defective seal  35  is automatically removed from the assembly line to a discharge conveyor and scrapped.  
         [0021]     Generally, there is no leakage through the seal  35 , and the tube will pass to station  202 , where, as in the prior art, a closure cap  32  is applied to the completed tube  118  by rotating the closure cap  32  onto the threads of the neck of head  21 .