Abstract:
A heating apparatus may have a nozzle to direct heated air on an open end of a plastic tube. A clamping apparatus may have two clamping devices slidably disposed to clamp the heated open end of the plastic tube to fuse the tube wall adjacent the open end. A control processor may be connected to control movement and dwell time of the tube holder, and to control heat application and clamp spacing and time. A graph of a clamping force as a function of the dwell time can be displayed for comparison of successive tube sealing operations.

Description:
This is a continuation-in-part patent application of U.S. patent application Ser. No. 12/291,298 now abandoned, filed on Nov. 6, 2008. U.S. patent application Ser. No. 12/291,298 is pending. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to systems used to seal one end of a plastic tube that may be used to hold fluid products such as tooth paste, creams, lotions, grease and the like. The plastic tube may have a mouth end with a threaded cap or other closure element. The new system may have a tube sealing apparatus with various electronic sensing and control elements and may be combined with a tube seal and wall strength test apparatus. 
     Systems that may be used to fill flexible plastic tubes through an open end with a fluid product and then seal the open end may be currently known. These systems for high volume production may have a tube conveyor on which the tube open end may be oriented upwardly to receive product from a dispensing device. The tube may then be conveyed to a heating device such as a hot air blower to heat the plastic to a selected temperature approximately the melting point of the plastic and then be conveyed to a jaw clamping device to press or crimp the open end plastic wall together to heat seal the open end. 
     While this may be considered a relatively simple process, various parameters associated with plastic tubes, for example, thickness of walls or other dimensions, and plastic composition that may affect the melt flow index, may affect the quality of the tube heat seal. Currently known methods for producing product filled plastic tubes may not incorporate testing methods and apparatus to test plastic tubes to ensure the tubes will be properly sealed in production to avoid failure of the seal or the wall of a tube when delivered to the consumer. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to apparatus for plastic tube sealing and testing. A housing may have in a sealing chamber a tube sealing positioning apparatus with a tube holder slidable on a vertical guide from a lower portion to an upper portion to be positioned adjacent a heating apparatus and a clamping apparatus. The tube holder may be moved and positioned by a linear positioning device. The heating apparatus may have a nozzle to direct heated air on an open end of a plastic tube. The clamping apparatus may have two clamping devices slidably disposed to clamp the heated open end of the plastic tube to fuse the tube wall adjacent the open end. A spacing distance sensor and a tube position distance sensor may be attached to the clamping devices for sensing the position of the tube and the spacing of the clamp jaws of the clamping devise. A control processor may be connected to the linear positioning device to control movement and dwell time of the tube holder. The heating apparatus and clamp positioning device may be connected to the control processor to control heat application and clamp jaw spacing and clamp time. A sealed tube may be attached to a top cover of a test container to be positioned in the test container. A sealing disk may be positioned on the top cover to close an aperture in the cover. The sealing disk may have a port to direct a fluid pressure into a mouth of the tube and a port to apply a vacuum to the test container. The control processor may control the amount of pressure or vacuum applied on a time basis for conducting a test. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a front elevation view with the front panel cut away showing the major electro-mechanical elements of a plastic tube sealing and test system according to an embodiment of the invention; 
         FIG. 2  illustrates a side elevation view with side panel removed of the system according to an embodiment of the invention; 
         FIG. 3  illustrates a top view with the top panel removed of a portion of the electro-mechanical elements of the system according to an embodiment of the invention; 
         FIG. 4  illustrates a schematic of the electrical and fluid elements of the system according to an embodiment of the invention; 
         FIG. 5  illustrates a schematic of the tube sealing apparatus according to an embodiment of the invention; 
         FIG. 6  illustrates a schematic of a tube heating apparatus according to an embodiment of the invention; 
         FIG. 7  illustrates a schematic of a clamping apparatus with a tube positioned in a heater nozzle according to an embodiment of the invention; 
         FIG. 8  illustrates a schematic of a clamping apparatus with a tube positioned in opposed clamp jaws according to an embodiment of the invention; 
         FIG. 9  illustrates a graph of the sealing pressure versus time for sealing a tube according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description represents the best currently contemplated modes for carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention. 
     Referring to  FIGS. 1 through 9 , a tube sealing apparatus  12  is illustrated as positioned in the left portion of a combined tube sealing and test system  10  enclosure or housing and a tube seal and wall strength test apparatus  14  is illustrated as positioned in the right portion. While for purposes of this description the two apparatus  12 ,  14  are illustrated in a combined housing  16 , it may be understood that each may also be used separately for purposes such as sealing tubes in an assembly operation if modified or testing tubes sealed for example on an assembly line. 
     The tube sealing apparatus  12  may have a tube sealing positioning apparatus  20  with a tube holder  22  slideably attached to a vertical guide  24  that extends from a generally lower portion  36  of the sealing chamber  18  to an upper portion  38  adjacent a tube heating apparatus  40 . The tube holder  22  may be raised and lowered in the sealing chamber  18  using a hydraulic or pneumatic device, an electric motor device or other suitable linear positioning device  122 . The tube holder  22  may have a generally horizontal holder  26  for receipt of a tube mouth end fixture  28  into which the mouth end  102  of a plastic tube  100  may be inserted. Multiple fixtures  28  may be used that may be sized to receive various shapes and sizes of tube mouth ends  102  including the cap  104  of a tube  100  if attached to the mouth end  102 . 
     The tube heating apparatus  40  may be positioned in the upper portion  38  of the sealing chamber  18  positioned for a plastic tube  100  raised by the tube holder  22  to have the open end  106  positioned adjacent a heater nozzle  42  of an air heater element  46 . The heater nozzle  42  may be a replaceable or interchangeable attached nozzle to allow attachment of nozzle sizes and shapes to mate with different configuration plastic tubes  100 . The heating device  46  may be an electric heating element that is controlled by heater control module  125 . The heating device  46  receives air from an air blower or compressed air  130  from an air flow control device  124  as may be understood in the art that may be controlled by a processor  120  that may be a digital processor, microprocessor, computer or the like that may be connected to a display device  121 . A cooling ring  44  may be positioned around the heating nozzle  42  as an element to cool the outside wall  108  of the plastic tube  100 . Cooling water is input at inlet port  114  and is circulated around cooling ring  44 . The water temperature is monitored by temperature sensors  116 . The flow rate of water is monitored by water pressure sensor  99  and the water exits the tube heating apparatus through outlet port  115 . The hot air is removed from the area around the cooling ring  44  with the aid of a negative air pressure device  111  such as a fan or air venture mounted on top of the heating device  46 . The air flow is controlled by air flow controller  112  and the amount of air is measured by air flow sensor  113 . The heated air exits the heating device  46  through the negative pressure device  111  and exit port  118 . 
     Intermediate the tube positioning apparatus  20  and the heating apparatus  40 , a clamping apparatus  50  or crimping apparatus may be positioned to press or crimp the open end  106  plastic wall  108  to fuse the open end in a heat seal manner. The clamping apparatus  50  may have one or more generally horizontal bars  52  attached to opposed frames  70  of the housing  16 . Two opposed clamping devices  54  may be slidably mounted on the bars  52  and may be moved from an open position  56  to an approximately closed position  58  by a lever arm device  60  that rotates on fixed pins  61 . The lever arm device  60  has the structure of a toggle clamp action wherein the members  65 ,  67  are attached to cross member  59  to be toggle clamp powered by a clamp positioning device  126 , for example, a hydraulic or pneumatic actuator. The clamping apparatus  50  moves the clamping devices  54  to a position  58  as controlled by fixed stops  133 . 
     The opposed clamping devices  54  may each have a clamping or sealing jaw  62  located to be positioned adjacent to each other at a distance commanded by the processor  120 . The spacing distance of the two jaws  62  when moved to a position adjacent may be calculated based on the parameters of each type of plastic tube  100 . For purposes of positioning and control the clamping devices  54  may have a spacing distance sensor  64  such as a laser gap sensor and may have a tube position sensor  66  such as an optical sensor to detect the top of the open end  106  of a tube  100 . 
     The tube sealing apparatus  12  may have a plastic tube  100  positioned on the tube holder  22 ; the tube holder  22  may be raised until the open end  106  of the tube  100  is sensed by the tube position sensor  66  that is connected to the processor  120 . The sensor  66  is used to determine the distance to the heater nozzle  42  or the distance from the tube holder  22  to the open end  106 ; the tube holder  22  may then be moved to place the open end  106  adjacent the heater nozzle  42  to heat the tube  100  for a defined time; when the defined time has elapsed, the tube  100  may be lowered to position the tube wall  108  area adjacent the open end  106  between the jaws  62 ; and the jaws  62  may be closed to a predetermined distance and maintained in a clamped position for a predetermined time to seal the tube  100 . As clamp jaws  62  close on the tube  100 , pre-fold jaws  144  shape the tube  100  from a round to an oval form insuring both an aesthetic and uniform seal. The pre-fold jaws  144  are adjustable and calibrated to provide validation for future sealing process setup. There is a selector wheel  73  to adjust the angle of the pre-fold jaws  144  relative to vertical. The sealing jaws  62  are attached to sealing jaw holder  63 . The sealing jaws  62  and sealing jaw holder  63  may have one or both holders  63  attached to the jaw support blocks  143  by a pivot pin  76  to allow the sealing jaws  62  to be non-parallel when a tube  100  is therebetween to allow for tube wall  108  thickness variations. A vernier dial with post  78  and a tab stop  79  allows small and repeatable adjustments of the relative angle of a sealing jaw  62 . A tube  100  sealed in this process may then be tested in a vacuum or pressure chamber apparatus to determine the strength of the sealed tube  100 . 
     The processor  120  may have software or firmware modules for controlling the tube holder  22  movement and positioning, for example, a loop crimping gap setting module, that receives signals from the spacing distance sensor  64  and a stepper motor control device  68  that may control an electric motor  69  to move the clamping apparatus  50 . An operator may enter the desired gap, or distance between clamp jaws  62 , at the operator interface  121 . The opposing clamp device  54  close to a position  58  resting on hard stops  133 . The motor  69  turns a threaded shaft  140  in a threaded nut  141  to push jaw support block  143  to the desired gap setting position. The jaw support block  143  slides on the slide bearing assembly  142 . There may also be parts per minute based timing for sealing process module  74  to control the time for tube  100  heating and for jaw  62  clamp time to simulate production cycling for tube sealing as well as to vary timing to test improved sealing parameters or marginal production process times. There may be temperature control program modules to sense and allow control of hot air temperature  125  or fluid control for heating the tube  100 . A data processing software module may control and collect data, such as crimp gap during crimping, temperature during tube heating and heating change during crimping time. 
     A sensor that may be a load force sensing device  145  may be attached to the threaded nut  141  and may be connected to the control processor  120 . When the clamping devices  54  are positioned against the hard stops  133  the force of the clamp jaws  62  against a tube  100  while in the second adjacent closed position  58  is transferred to the jaw support block  143  and thereby to the load force sensing device  145  that converts the load force to a signal that is transmitted to the control processor  120 . The parameters of time for clamp jaws  62  in the first spaced apart position  56  and the second adjacent closed position  58  and the load force when in the second adjacent closed position as recorded by the control processor may be displayed in a graphical form of the load force, Y-axis, versus the tube processing time, X-axis. This graphical representation may display the dwell time during tube sealing during which time the interior wall of a tube  100  melts and welds together and the combined wall thickness of the sealed end reduces with a resultant measured pressure decrease of the clamp jaws  62 . This is illustrated as a decreasing slope during dwell time on  FIG. 9 . These parameter characteristics are caused by factors of temperature, tube materials and structure, jaw gap and the like. The parameters as may be displayed graphically as illustrated in  FIG. 9  may be used as a template, when proper sealing parameters for desired sealing results for a type of tube have been determined, to compare to measured parameters for subsequent tube sealing operation of an apparatus to monitor proper operation. 
     A tube seal and wall strength test apparatus  14  may be used in a stand alone test station to test tubes  100  or may be integrated with a tube sealing apparatus  14  as illustrated in the Drawings. The tube test apparatus  14  may have a test container  80  that may be generally cylindrical in shape with a top cover  82  removable and having an attachment aperture  84  therein for threadable attachment of a threaded mouth  110  of a plastic tube  100 . 
     The top cover  82  and attachment aperture  84  may have other attachment mechanisms for attachment of non-threaded tubes  100 . A tube  100  may be attached at a mouth end  102  in the attachment aperture  84  and the top cover  82  may be placed on the test container  80  with the tube  100  in the test container  80 . The test container  80  may then be positioned in the tube test apparatus  14 . A sealing disk  86  controlled by a position activator  88 , such as a hydraulic or pneumatic piston, may be positioned on the top cover  82  to close the aperture  84 . The sealing disk  86  may have one or more ports  90  in communication with the tube mouth  100  to allow fluid pressure to be applied to the interior of the tube  100  and with the interior of the test container  80  to allow a vacuum to be applied in the test container  80 . The ports  90  may be connected to a vacuum pump or venturi  128  and a fluid, for example, compressed air, source  130 . 
     The processor  120  may have software or firmware modules for controlling the test apparatus  14  pressure and vacuum testing, for example, a module to allow entering; pressure and vacuum set points, speed of ramp up to pressure or vacuum, and dwell time at set points. There may be a data output of the vacuum transmitter  92  and pressure transmitter  94  to the processor  120  for use in control of vacuum and pressure and to detect a sudden change when a tube  100  fails or there may be a leak of pressure or vacuum. A data processing software module may control and collect data, such as failure pressure or vacuum, test time and time of failure, and failure type that may be entered by a user to indicate tube wall or tube seal failure. 
     The tube test system  10  may have a display  121  on the front panel  72  for use in display of apparatus settings, test results, switch images for touch panel control, as well as display of other elements, for example, an internal processor  120  program functions and status. An emergency stop switch  132  and an on/off switch  134  may also be located on the front panel. The sealing chamber  18  and test chamber  19  may have movable doors for closing to protect a user from any unexpected circumstances. The doors may have sensors  98  that signal the processor  120  to inhibit operation of the tube sealing apparatus  12  and test apparatus  14  if the door is not closed. Also, a water pressure sensor  99  may signal the processor  120  to turn off the heating apparatus  40 . The processor  120  may be programmed to return the horizontal holder  26  to the lower portion  36  of the sealing chamber  18  at the end of the sealing process or if the sealing process is interrupted. These processes may be considered to be safety features. 
     The positioning of the tube sealing apparatus  12  elements may be useful for production of sealed product tubes  100 . Current practice appears to move tubes from a heating station to a sealing station. This two step process may not be as repetitively reliable as the combination heating and sealing in one apparatus as described. 
     While the invention has been particularly shown and described with respect to the illustrated embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.