Plastic tube sealing and test system

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.

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.

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 toFIGS. 1 through 9, a tube sealing apparatus12is illustrated as positioned in the left portion of a combined tube sealing and test system10enclosure or housing and a tube seal and wall strength test apparatus14is illustrated as positioned in the right portion. While for purposes of this description the two apparatus12,14are illustrated in a combined housing16, 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 apparatus12may have a tube sealing positioning apparatus20with a tube holder22slideably attached to a vertical guide24that extends from a generally lower portion36of the sealing chamber18to an upper portion38adjacent a tube heating apparatus40. The tube holder22may be raised and lowered in the sealing chamber18using a hydraulic or pneumatic device, an electric motor device or other suitable linear positioning device122. The tube holder22may have a generally horizontal holder26for receipt of a tube mouth end fixture28into which the mouth end102of a plastic tube100may be inserted. Multiple fixtures28may be used that may be sized to receive various shapes and sizes of tube mouth ends102including the cap104of a tube100if attached to the mouth end102.

The tube heating apparatus40may be positioned in the upper portion38of the sealing chamber18positioned for a plastic tube100raised by the tube holder22to have the open end106positioned adjacent a heater nozzle42of an air heater element46. The heater nozzle42may be a replaceable or interchangeable attached nozzle to allow attachment of nozzle sizes and shapes to mate with different configuration plastic tubes100. The heating device46may be an electric heating element that is controlled by heater control module125. The heating device46receives air from an air blower or compressed air130from an air flow control device124as may be understood in the art that may be controlled by a processor120that may be a digital processor, microprocessor, computer or the like that may be connected to a display device121. A cooling ring44may be positioned around the heating nozzle42as an element to cool the outside wall108of the plastic tube100. Cooling water is input at inlet port114and is circulated around cooling ring44. The water temperature is monitored by temperature sensors116. The flow rate of water is monitored by water pressure sensor99and the water exits the tube heating apparatus through outlet port115. The hot air is removed from the area around the cooling ring44with the aid of a negative air pressure device111such as a fan or air venture mounted on top of the heating device46. The air flow is controlled by air flow controller112and the amount of air is measured by air flow sensor113. The heated air exits the heating device46through the negative pressure device111and exit port118.

The opposed clamping devices54may each have a clamping or sealing jaw62located to be positioned adjacent to each other at a distance commanded by the processor120. The spacing distance of the two jaws62when moved to a position adjacent may be calculated based on the parameters of each type of plastic tube100. For purposes of positioning and control the clamping devices54may have a spacing distance sensor64such as a laser gap sensor and may have a tube position sensor66such as an optical sensor to detect the top of the open end106of a tube100.

The tube sealing apparatus12may have a plastic tube100positioned on the tube holder22; the tube holder22may be raised until the open end106of the tube100is sensed by the tube position sensor66that is connected to the processor120. The sensor66is used to determine the distance to the heater nozzle42or the distance from the tube holder22to the open end106; the tube holder22may then be moved to place the open end106adjacent the heater nozzle42to heat the tube100for a defined time; when the defined time has elapsed, the tube100may be lowered to position the tube wall108area adjacent the open end106between the jaws62; and the jaws62may be closed to a predetermined distance and maintained in a clamped position for a predetermined time to seal the tube100. As clamp jaws62close on the tube100, pre-fold jaws144shape the tube100from a round to an oval form insuring both an aesthetic and uniform seal. The pre-fold jaws144are adjustable and calibrated to provide validation for future sealing process setup. There is a selector wheel73to adjust the angle of the pre-fold jaws144relative to vertical. The sealing jaws62are attached to sealing jaw holder63. The sealing jaws62and sealing jaw holder63may have one or both holders63attached to the jaw support blocks143by a pivot pin76to allow the sealing jaws62to be non-parallel when a tube100is therebetween to allow for tube wall108thickness variations. A vernier dial with post78and a tab stop79allows small and repeatable adjustments of the relative angle of a sealing jaw62. A tube100sealed in this process may then be tested in a vacuum or pressure chamber apparatus to determine the strength of the sealed tube100.

The processor120may have software or firmware modules for controlling the tube holder22movement and positioning, for example, a loop crimping gap setting module, that receives signals from the spacing distance sensor64and a stepper motor control device68that may control an electric motor69to move the clamping apparatus50. An operator may enter the desired gap, or distance between clamp jaws62, at the operator interface121. The opposing clamp device54close to a position58resting on hard stops133. The motor69turns a threaded shaft140in a threaded nut141to push jaw support block143to the desired gap setting position. The jaw support block143slides on the slide bearing assembly142. There may also be parts per minute based timing for sealing process module74to control the time for tube100heating and for jaw62clamp 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 temperature125or fluid control for heating the tube100. 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 device145may be attached to the threaded nut141and may be connected to the control processor120. When the clamping devices54are positioned against the hard stops133the force of the clamp jaws62against a tube100while in the second adjacent closed position58is transferred to the jaw support block143and thereby to the load force sensing device145that converts the load force to a signal that is transmitted to the control processor120. The parameters of time for clamp jaws62in the first spaced apart position56and the second adjacent closed position58and 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 tube100melts and welds together and the combined wall thickness of the sealed end reduces with a resultant measured pressure decrease of the clamp jaws62. This is illustrated as a decreasing slope during dwell time onFIG. 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 inFIG. 9may 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 apparatus14may be used in a stand alone test station to test tubes100or may be integrated with a tube sealing apparatus14as illustrated in the Drawings. The tube test apparatus14may have a test container80that may be generally cylindrical in shape with a top cover82removable and having an attachment aperture84therein for threadable attachment of a threaded mouth110of a plastic tube100.

The top cover82and attachment aperture84may have other attachment mechanisms for attachment of non-threaded tubes100. A tube100may be attached at a mouth end102in the attachment aperture84and the top cover82may be placed on the test container80with the tube100in the test container80. The test container80may then be positioned in the tube test apparatus14. A sealing disk86controlled by a position activator88, such as a hydraulic or pneumatic piston, may be positioned on the top cover82to close the aperture84. The sealing disk86may have one or more ports90in communication with the tube mouth100to allow fluid pressure to be applied to the interior of the tube100and with the interior of the test container80to allow a vacuum to be applied in the test container80. The ports90may be connected to a vacuum pump or venturi128and a fluid, for example, compressed air, source130.

The processor120may have software or firmware modules for controlling the test apparatus14pressure 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 transmitter92and pressure transmitter94to the processor120for use in control of vacuum and pressure and to detect a sudden change when a tube100fails 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 system10may have a display121on the front panel72for 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 processor120program functions and status. An emergency stop switch132and an on/off switch134may also be located on the front panel. The sealing chamber18and test chamber19may have movable doors for closing to protect a user from any unexpected circumstances. The doors may have sensors98that signal the processor120to inhibit operation of the tube sealing apparatus12and test apparatus14if the door is not closed. Also, a water pressure sensor99may signal the processor120to turn off the heating apparatus40. The processor120may be programmed to return the horizontal holder26to the lower portion36of the sealing chamber18at 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 apparatus12elements may be useful for production of sealed product tubes100. 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.