Film side sealing apparatus with closed-loop temperature control of a heater
A side sealing apparatus for a shrink packaging machine comprising closed loop temperature control of a heater for maintaining an optimum temperature for cutting and sealing two layers of thermoplastic film. The heater comprises a cable or cartridge heater with an internal thermocouple, and it is connected to an automatic temperature controller. The heater is mounted on the side sealer apparatus between two sets of top and bottom V-belts mounted around drive rolls and idler rolls. The V-belts provide nip pressure against the film in order to drive the film. In one embodiment, nip pressure is generated by nip rollers on the scrap side of the film, and by low friction belt support guides on the package side of the film. In another embodiment, the belt support guides are replaced with a series of upper and lower nip rollers, and adjustable toggle clamps provide adjustable pressure on the series of upper and lower nip rollers.
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This application is a Continuation-In-Part of prior application Ser. No. 10/994,691, filed Nov. 22, 2004, now pending which is herein incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates generally to a side sealer of thermoplastic film around a dimensioned article, and in particular to a side sealing apparatus having an internally heated sealing bar integrated with a closed-loop temperature controller operating essentially in free air supported by thin clips in order to minimize heat transfer to the overall assembly, allowing the heater to cut and seal a thermoplastic film in as tight a temperature range as possible, while allowing the overall temperature of the entire unit to operate at close to room temperature.
2. Description of Related Art
A commonly used side sealer of thermoplastic film in shrink wrapping machines comprises dual hot wires. The hot wires are typically two (2) eight inch heated nichrome wires mounted parallel, one on top of the other. The wires are separated by a gap of approximately 0.010 inches to 0.015 inches (the thickness of an average business card). Adjusting and maintaining this gap is critical for proper sealing and cutting of the film web as this film is cut and sealed by radiant heat from the opposing wires. The wires utilized in this arrangement must be installed completely flat against the backing material, in this case, 1 inch long ceramic “beads” or blocks. No bowing or slight kinks in the wires can be tolerated as a uniform gap must be maintained. Access to these wires requires removal of cover plates and film drive belts. Frequent cleaning of resin buildup is necessary. Cleaning the wires without disturbing the gap setting or flatness of the wire is very difficult. Readjustment of the gap is usually necessary. All of this results in lost production time.
Further, the performance of the dual side sealer is often not stable over extended periods of operation even when initially adjusted to optimum settings. A significant cause of this instability is the drift in wire temperatures over time due to drifts in power conditions typical in many factories. The wire temperature is subject to open loop control, i.e. any changes in factory power feed conditions or operating conditions will cause the wire temperature to change, and conversely, will require an operator to manually adjust the electrical power values to the wire power feed in order to bring the wire temperature back to the desired sealing temperature. Another inherent problem with the dual wire side sealer is the fact that many side sealer components heat up to undesirably high temperatures during operation of the side sealer as a result of the sealing wires radiating heat and its mounting being in contact with the frame they are mounted on which conducts heat to the main assembly resulting in resin build-up during production runs. The heat build-up is detrimental to successful side sealing requiring frequent stopping of the machine in order to clean the molten film build-up on the individual wire assemblies. The resin build-up is a result of unintentional heating of the area of the film that is close to, but outside of, the actual seal area. This unintentionally heated film becomes soft and is prone to stick to components that it contacts, particularly if the side sealer frame components are already at an elevated temperature. In addition, the dual wire side sealer has a large parts count, and coupled with the fact that it operates at an overall elevated temperature, the side sealer belts and bearings are subject to frequent failure, resulting in attendant high maintenance costs. In addition, when the dual wire sealer is inoperable for any reason, it requires sufficient time to cool down in order to restore its operation due to the excessive operating temperature of the entire unit, which frequently reaches temperatures of 135 degrees F. A typical cleaning and resetting will take at least 1 hour, resulting in lost production for that period of time.
Prior art patents include U.S. Pat. No. 6,526,728 issued Mar. 4, 2003 to Gregg R. Sorenson et al. and assigned to Conflex Incorporated of Milwaukee, Wis. discloses a thermoplastic film side sealing mechanism comprising a hot wire assembly having a hot wire mounted between a stationary mounting block and a pivoting mounting block. The hot wire also diverges at an angle which is about 0.32 inches over an 8.125 inch run. The divergence is at an angle relative to the path of forwardly disposed belts. The pivoting mounting block provides for releasing tension of the wire to allow quick and easy removal of the wire ends from the assembly clamps. However, there is no closed loop control of the temperature of the hot wire and resin build-up occurs requiring frequent maintenance.
SUMMARY OF THE INVENTIONAccordingly, it is therefore an object of this invention to provide a closed loop temperature controller for precise temperature control of a heater that directly contacts the film to cut and seal on a side sealer.
It is a further object of this invention to provide low coefficient of friction belt support plates or guides on the package side of the sealer to generate nip pressure between top and bottom V-belts which exert nip pressure against the film to drive the film.
It is another object of this invention to provide a side sealer apparatus having an upper series of nip rollers and a lower series of nip rollers in contact with the V-belts for generating a nip pressure to drive the film wherein the nip pressure provided by the upper series of nip rollers is adjustable by means of a toggle clamp.
It is another object of this invention to provide a heat source that closely approximates an ideal sealing temperature of a particular thermoplastic film with a given thickness, and the heat source that cuts the film will operate at precisely the ideal temperature so as to produce consistent film strength seals with no residue and pleasing aesthetics with a wide range of thermoplastic materials, which is not possible with present technology.
It is another object of this invention to provide a simplified side sealer of thermoplastic film by attaching a temperature controlled heater having an internal or external thermocouple in the path of the film for sealing the film on a side of a product that requires no adjustment other than setting the required temperature for sealing a particular film type and gauge at a specific speed.
It is a further object of this invention to provide a method for sealing a thermoplastic film covering a product by using an elongated heater attached to a closed loop temperature controller and mounting the heater at an angle in the path of the film near the edges to be sealed.
These and other objects are accomplished by a side sealer apparatus for cutting and sealing two layers of film together near an edge of heat-sealable material comprising, means for moving the heat sealable material through the side sealer apparatus, means, attached to the side sealer in the path of heat-sealable material, for generating heat to cut and seal the heat-sealable material near the edge, means connected to the heat generating means for providing closed loop control of the heat generating means in accordance with a predetermined heat setting, a top drive roll spaced-apart from a top idler roll on a side of said apparatus above said moving means, a bottom drive roll spaced-apart from a bottom idler roll and positioned immediately under the top drive roll and top idler roll respectively, a first pair of spaced-apart V-belts positioned around and between the top drive roll and the top idler roll on a side of the apparatus above the moving means, a second pair of spaced-apart V-belts positioned around and between the bottom driver roll and the bottom idler roll, a top belt guide, having a low coefficient of friction and a bottom groove for a lower portion of an outer one of the first pair of spaced apart V-belts to travel in, to provide nip pressure on the heat sealable material, and a bottom belt guide, having a low coefficient of friction and a top groove for an upper portion of an outer one of the second pair of spaced apart V-belts to travel in, to provide nip pressure on the heat sealable material. The heat generating means is mounted on the side sealer apparatus at a predetermined angle relative to horizontal between the V-belts positioned on an inner side of the heater and the V-belts positioned on an outer side of the heater. The heat-sealable material comprises a thermoplastic film. The heat generating means comprises an elongated metal sheathed body including an internal heating mechanism and a thermocouple. The moving means comprises a conveyor.
The objects are further accomplished by a side sealer apparatus for cutting and sealing of heat-sealable film together near an edge comprising a means attached to the side sealer apparatus in the path of the heat-sealable film for generating heat to cut and seal the heat-sealable film together near the edge, a top drive roll spaced-apart from a top idler roll, a bottom drive roll spaced-apart from a bottom idler roll and positioned immediately under the top drive roll and the top idler roll respectively, a first pair of spaced-apart V-belts positioned around and between the top drive roll and the top idler roll on a side of the apparatus above the moving means, a second pair of spaced-apart V-belts positioned around and between the bottom driver roll and the bottom idler roll, a plurality of pairs of upper nip rollers positioned between the top drive roll and the top idler roll and in contact with a lower portion of the first pair of spaced-apart V-belts, a plurality of pairs of lower nip rollers positioned between the bottom drive roll and the bottom idler roll and in contact with an upper portion of the second pair of spaced-apart V-belts, and means for providing an adjustable nip pressure on the pairs of upper nip rollers in contact with the first pair of spaced-apart V-belts. The side sealer apparatus comprises a conveyor for moving the heat-sealable film through the apparatus. The heat generating means comprises an elongated metal sheathed body including an internal heating mechanism and a thermocouple. The heat-sealable film comprises a thermoplastic film. The heat generating means is mounted on the side sealer apparatus at a predetermined angle relative to horizontal between one of the V-belts positioned on an inner side of the heater and one of the V-belts positioned on an outer side of the heater. The apparatus comprises means connected to the heat generating means for providing closed loop control of the heat generating means in accordance with a predetermined heat setting. The means for providing an adjustable nip pressure on the pairs of upper nip rollers in contact with the first pair of spaced-apart V-belts comprises a nip roller mounting frame for holding the upper nip rollers in a horizontal row, the nip roller mounting frame being attached to a wall of the side sealer via a hinge, and means for applying pressure to an upper surface of the nip roller mounting frame. The pressure applying means comprises at least one toggle clamp having a leg extending to and in contact with the upper surface of the nip roller mounting frame.
These objects are further accomplished by providing a method for cutting and sealing two layers of heat-sealable film together near an edge in a side sealer apparatus comprising the steps of moving the heat-sealable film through the side sealer apparatus, generating heat to cut and seal the heat-sealable film together near the edge with means attached to the side sealer apparatus in the path of the film, providing a top drive roll spaced-apart from a top idler roll on the side sealer apparatus, providing a bottom drive roll spaced-apart from a bottom idler roll on the side sealer and positioned immediately under the top drive roll and the top idler roll respectively, positioning a first pair of spaced-apart V-belts around and between the top drive roll and the top idler roll on a side of the side sealer apparatus above the means for moving the film, positioning a second pair of spaced-apart V-belts around and between the bottom driver roll and the bottom idler roll, attaching a plurality of pairs of upper nip rollers between the top drive roll and the top idler roll and in contact with a lower portion of the first pair of spaced-apart V-belts, attaching a plurality of pairs of lower nip rollers between the bottom drive roll and the bottom idler roll and in contact with an upper portion of the second pair of spaced-apart V-belts, and providing an adjustable nip pressure on the pairs of upper nip rollers in contact with the first pair of spaced-apart V-belts.
Additional objects, features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.
BRIEF DESCRIPTION OF THE DRAWINGSThe appended claims particularly point out and distinctly claim the subject matter of this invention. The various objects, advantages and novel features of this invention will be more fully apparent from a reading of the following detailed description in conjunction with the accompanying drawings in which like reference numerals refer to like parts, and in which:
Referring to
The side sealer 10 comprises an upper series of nip rolls 24a-24e and a lower series of nip rolls 26a-26e mounted directly under the upper series of nip rolls 24a-24e. The V-belts need to exert a “nip” pressure against the film 42 in order to drive the film 42. The nip rolls 24a-24e and 26a-26e are used to generate the nip pressure on the top and bottom scrap side V-belts 15 and 21. However, belt support plates or guides 25, 27 (
Referring now to
When an electrical current is applied to the heater 28 via wires 34a, 34b, the internal mechanism generates heat that is efficiently transferred to the metal sheath of the heater 28. By varying the electrical power to the heater 28, the temperature of the heater 28 can be increased or decreased. The heater replaces pairs of nichrome resistive wires used in prior art open loop dual wire systems. It also replaces other methods of cutting and sealing of films on side sealer equipment. In operation the two layers of the film 42 that are to be cut and sealed together are guided into intimate and precise contact with the heater 28. Heat is efficiently transferred from the heater 28 to the film 42 producing a strong, consistent seal.
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In order to minimize frictional forces, the top belt guide 25 and the bottom belt guide 27 are made from a Delrin® plastic such as Delrin® 15OE Homopolymer having a maximum continuous use temperature of 185 degrees Fahrenheit and a dynamic coefficient of friction of 0.20. It is manufactured by UNITAL. Other manufacturers of low friction, high temperature plastic materials may be substituted to embody the belt guide 25, 27.
Second Alternate Embodiment Referring to
Referring to
Referring to
There is substantially no drag between the V-belts 15, 16, 21, 22 and the series of upper and lower nip rollers in
Referring now to
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This invention has been disclosed in terms of certain embodiments. It will be apparent that many modifications can be made to the disclosed apparatus without departing from the invention. Therefore, it is the intent of the appended claims to cover all such variations and modifications as come within the true spirit and scope of this invention.
Claims
1. A side sealer apparatus for cutting and sealing two layers of film together near an edge of heat-sealable material comprising:
- means for moving the heat-sealable material through the side sealer apparatus;
- means attached to said side sealer apparatus in the path of said heat-sealable material for generating heat to cut and seal said heat-sealable material near said edge;
- a top drive roll spaced-apart from a top idler roll;
- a bottom drive roll spaced-apart from a bottom idler roll and positioned immediately under the top drive roll and top idler roll respectively;
- a first pair of spaced-apart V-belts positioned around and between the top drive roll and the top idler roll on a side of the apparatus above the moving means;
- a second pair of spaced-apart V-belts positioned around and between the bottom driver roll and the bottom idler roll;
- a top belt guide, having a low coefficient of friction and a bottom groove for a lower portion of an outer one of the first pair of spaced apart V-belts to travel in, to provide nip pressure on the heat-sealable material; and
- a bottom belt guide, having a low coefficient of friction and a top groove for an upper portion of an outer one of the second pair of spaced apart V-belts to travel in, to provide nip pressure on the heat-sealable material.
2. The side sealer apparatus as recited in claim 1 wherein:
- said heat generating means is mounted on said side sealer apparatus at a predetermined angle relative to horizontal between the V-belts positioned on an inner side of the heater and the V-belts positioned on an outer side of the heater.
3. The side sealer apparatus as recited in claim 1 wherein said heat-sealable material comprises a thermoplastic film.
4. The side sealer apparatus as recited in claim 1 wherein said heat generating means comprises an elongated metal sheathed body including an internal heating mechanism and a thermocouple.
5. The side sealer apparatus as recited in claim 1 wherein said moving means comprises a conveyor.
6. The side sealer apparatus as recited in claim 1, wherein said apparatus comprises means connected to said heat generating means for providing closed loop control of said heat generating means in accordance with a predetermined heat setting.
7. A side sealer apparatus for cutting and sealing two layers of heat-sealable film together near an edge comprising:
- means for moving the heat-sealable material through said side sealer apparatus;
- means attached to said side sealer apparatus in the path of said heat-sealable film for generating heat to cut and seal said heat-sealable film together near said edges;
- a top drive roll spaced-apart from a top idler roll;
- a bottom drive roll spaced-apart from a bottom idler roll and positioned immediately under said top drive roll and said top idler roll respectively;
- a first pair of spaced-apart V-belts positioned around and between said top drive roll and said top idler roll on a side of the apparatus above the moving means;
- a second pair of spaced-apart V-belts positioned around and between said bottom driver roll and said bottom idler roll;
- a plurality of pairs of upper nip rollers positioned between said top drive roll and said top idler roll and in contact with a lower portion of said first pair of spaced-apart V-belts;
- a plurality of pairs of lower nip rollers positioned between said bottom drive roll and said bottom idler roll and in contact with an upper portion of said second pair of spaced-apart V-belts; and
- means for providing an adjustable nip pressure on said pairs of upper nip rollers in contact with said first pair of spaced-apart V-belts.
8. The side sealer apparatus as recited in claim 7 wherein said moving means comprises a conveyor.
9. The side sealer apparatus as recited in claim 7 wherein said heat generating means comprises an elongated metal sheathed body including an internal heating mechanism and a thermocouple.
10. The side sealer apparatus as recited in claim 7 wherein said heat-sealable film comprises a thermoplastic film.
11. The side sealer apparatus as recited in claim 7 wherein:
- said heat generating means is mounted on said side sealer apparatus at a predetermined angle relative to horizontal between one of said V-belts positioned on an inner side of the heater and one of said V-belts positioned on an outer side of the heater.
12. The side sealer apparatus as recited in claim 7, wherein said apparatus comprises means connected to said heat generating means for providing closed loop control of said heat generating means in accordance with a predetermined heat setting.
13. The side sealer apparatus as recited in claim 7 wherein said means for providing an adjustable nip pressure on said pairs of upper nip rollers in contact with said first pair of spaced-apart V-belts comprises:
- a nip roller mounting frame for holding said upper nip rollers in a horizontal row, said nip roller mounting frame being attached to a wall of said side sealer via a hinge; and
- means for applying pressure to an upper surface of said nip roller mounting frame to produce said adjustable nip pressure.
14. The side sealer as recited in claim 13, wherein said pressure applying means comprises at least one toggle clamp having a leg extending to and in contact with said upper surface of said nip roller mounting frame.
15. A side sealer apparatus for cutting and sealing of heat-sealable film together near an edge comprising:
- means attached to said side sealer apparatus in a path of said heat-sealable film for generating heat to cut and seal said heat-sealable film together near an edge;
- a top drive roll spaced-apart from a top idler roll;
- a bottom drive roll spaced-apart from a bottom idler roll and positioned immediately under said top drive roll and said top idler roll respectively;
- a first pair of spaced-apart V-belts positioned around and between said top drive roll and said top idler roll on a side of the apparatus above the moving means;
- a second pair of spaced-apart V-belts positioned around and between said bottom driver roll and said bottom idler roll;
- a plurality of pairs of upper nip rollers positioned between said top drive roll and said top idler roll and in contact with a lower portion of said first pair of spaced-apart V-belts;
- a plurality of pairs of lower nip rollers positioned between said bottom drive roll and said bottom idler roll and in contact with an upper portion of said second pair of spaced-apart V-belts; and
- means for providing an adjustable nip pressure on said pairs of upper nip rollers in contact with said first pair of spaced-apart V-belts.
16. The side sealer apparatus as recited in claim 15, wherein said heat generating means comprises an elongated metal sheathed body including an internal heating mechanism and a thermocouple.
17. The side sealer apparatus as recited in claim 15, wherein said heat-sealable film comprises a thermoplastic film.
18. The side sealer apparatus as recited in claim 15 wherein:
- said heat generating means is mounted on said side sealer apparatus at a predetermined angle relative to horizontal between one of said V-belts positioned on an inner side of the heater and one of said V-belts positioned on an outer side of the heater.
19. The side sealer apparatus as recited in claim 15, wherein said apparatus comprises means connected to said heat generating means for providing closed loop control of said heat generating means in accordance with a predetermined heat setting.
20. The side sealer apparatus as recited in claim 15, wherein said means for providing an adjustable nip pressure on said pairs of upper nip rollers in contact with said first pair of spaced-apart V-belts comprises:
- a nip roller mounting frame for holding said upper nip rollers in a horizontal row, said nip roller mounting frame being attached to a wall of said side sealer via a hinge; and
- means for applying pressure to an upper surface of said nip roller mounting frame.
21. The side sealer as recited in claim 20, wherein said pressure applying means comprises at least one toggle clamp having a leg extending to and in contact with said upper surface of said nip roller mounting frame.
22. A method for cutting and sealing two layers of heat-sealable film together near an edge in a side sealer apparatus comprising the steps of:
- moving said heat-sealable film through said side sealer apparatus;
- generating heat to cut and seal said heat-sealable film together near said edge with means attached to said side sealer apparatus in the path of said film;
- providing a top drive roll spaced-apart from a top idler roll on said side sealer apparatus;
- providing a bottom drive roll spaced-apart from a bottom idler roll on said side sealer and positioned immediately under said top drive roll and said top idler roll respectively;
- positioning a first pair of spaced-apart V-belts around and between said top drive roll and said top idler roll on a side of said side sealer apparatus above said means for moving said film;
- positioning a second pair of spaced-apart V-belts around and between said bottom driver roll and said bottom idler roll;
- attaching a plurality of pairs of upper nip rollers between said top drive roll and said top idler roll and in contact with a lower portion of said first pair of spaced-apart V-belts;
- attaching a plurality of pairs of lower nip rollers between said bottom drive roll and said bottom idler roll and in contact with an upper portion of said second pair of spaced-apart V-belts; and
- providing an adjustable nip pressure on said pairs of upper nip rollers in contact with said first pair of spaced-apart V-belts.
23. The method as recited in claim 22 wherein said step of moving said heat-sealable film through said side sealer apparatus comprises the step of providing a conveyor.
24. The method as recited in claim 22 wherein said step of generating heat comprises the step of providing an elongated metal sheathed body including an internal heating mechanism and a thermocouple.
25. The method as recited in claim 22 wherein said method comprises the step of sealing thermoplastic film.
26. The method as recited in claim 22 wherein said step of generating heat comprises the step of mounting a heat generating means on said side sealer apparatus at a predetermined angle relative to horizontal between one of said V-belts positioned on an inner side of the heater and one of said V-belts positioned on an outer side of the heater.
27. The method as recited in claim 22 wherein said step of generating heat to cut and seal said heat-sealable film comprises the step of providing closed loop control of means for generating said heat in accordance with a predetermined heat setting heat setting.
28. The method as recited in claim 22 wherein said step of providing an adjustable nip pressure on said pairs of upper nip rollers in contact with said first pair of spaced-apart V-belts comprises the steps of:
- holding said upper nip rollers in a horizontal row with a nip roller mounting frame, said nip roller mounting frame being attached to a wall of said side sealer via a hinge; and
- applying pressure to an upper surface of said nip roller mounting frame to move said mounting frame downward and provide said adjustable nip pressure.
29. The method as recited in claim 28, wherein said step of applying pressure comprises the step of providing at least one toggle clamp having a leg extending to and in contact with said upper surface of said nip roller mounting frame.
Type: Application
Filed: Sep 22, 2005
Publication Date: May 25, 2006
Applicant:
Inventors: Frank James (Nashua, NH), Jeffrey Lindberg (Merrimack, NH), John Gilbert (Lowell, MA)
Application Number: 11/232,672
International Classification: B65B 7/02 (20060101);