Patent Application
20090156381
The present invention relates generally to the art of bag making and machines for making bags. More specifically, it relates to bag making and bag machines with seal bars and heat pipes.
There are many known bag machines. One style is a rotary drum machine. Rotary drum machines are well known, and found in U.S. Pat. Nos. 6,117,058, 4,934,993, 5,518,559, 5,587,032 and 4,642,084 (each of which is hereby incorporated by reference). Bag machine, as used herein, includes a machine used to make pouches bags such as draw tape bags, non-draw tape bags, and other bags.
A detailed description of the operation of rotary bag machines may be found in the patents above, or in prior art commercially available machines such as the CMD 1270GDS or 1503ED, but their general operation may be seen with respect to
The web is provided through dancer assembly 203 to drum 208. Drum 208 includes a plurality of seal bars 209. The seals bars are heated and create the seals forming the bags from web 201. The distance between seals created by the drum is related to the bag length (for bags formed end to end) or the bag width (for bags formed by making side seals). End to end bags are formed with one seal from the drum, and side to side bags are formed with a pair of seals. The drum diameter may be adjusted and/or less than all of the seal bars turned on to determine the distance between seals, and hence bag size.
After web 201 leaves drum 208 it is directed to rotary knife 218, which creates a perforation between bags, or could separate adjoining bags. Other downstream processing stations, such as winders, folders, etc.
Seal bars 209 can sometimes have multiple temperature zones, such as where a draw tape is being sealed. However, seal bars 209, as well as seal bars in other style machines, can develop unwanted localized hot spots. These hot spots can cause the film to thin or burn. The prior art has used heat pipes to reduce or avoid unwanted hot spots. Heat pipes are disposed within the seal bar, close to the heater. The heater is typically close to, but not on, the surface disposed to impart the seals to the film. The heat pipe could extend the entire length (cross machine direction) of the seal bar, or be in several sections for seal bars with multiple temperature zones. Surface disposed to impart a seal on a film, as used herein, includes a surface of any size or shape, and need not be flat.
Heat pipes (which are also used in other industries) are typically a sealed aluminum or copper container, and typically a cylinder in a bag making applications. The inner surface has a capillary wicking material and a liquid is in the pipe, which enters the capillaries, wetting all internal surfaces. Applying excess heat at a point along the surface of the pipe causes the liquid there to boil and enter a vapor state, which reduces temperature at that location. The gas moves inside the sealed pipe to a cooler location where it condenses, and heats that location via the condensing. Thus, heat is distributed from hot spots to cooler locations through convection and vaporization/condensing. Heat pipes can have an effective thermal conductivity much greater than that of copper. Heat pipes can be built in almost any size and shape. Heat pipes are commercially available from Noren®.
While some commercially available heat pipes are as described above, others are simpler, such as a closed container containing a liquid. Heat pipe as used herein, includes a pipe or container (which may be of any shape) used to transfer heat from one part of a seal bar to another to reduce the likelihood of hot spots on the seal bar.
If a heat pipe gets too hot, the pressure inside can cause a catastrophic failure—the heat pipe can explode. The prior art attempted to regulate the heat input into the seal bar to prevent overheating of the heat pipe. A thermocouple or other feedback device has been used, and when the seal bar or sensed temperature reached a threshold, the heat into the seal bar was temporarily reduced or ended. However, thermocouples and/or controls have failed, causing the heat pipe to catastrophically fail. Another attempt to prevent failure was to simply run the seal bars cooler, but this resulted in seals (and thus bags) not being properly made.
Accordingly, a heat pipe, and a bag machine having a heat pipe, that reduces or eliminates catastrophic failure, is desirable.
According to a first aspect of the invention a bag making machine includes an input section, a sealing section and an output section. The sealing section includes a seal bar having a heat pipe with a relief zone.
According to a second aspect of the invention a method of making bags includes receiving a film, applying at least one seal to the film and processing the film after sealing it. The sealing is done with a seal bar that has a heat pipe and pressure is relieved in the heat pipe through a relief zone when the pressure in the pipe near the relief zone substantially exceeds a desired level.
According to a third aspect of the invention a bag making machine includes an input section, a sealing section and an output section. The sealing section includes a seal bar having a heat pipe and the heat pipe has a means for relieving pressure within the heat pipe.
According to a fourth aspect of the invention a bag making machine includes an input section, a sealing section and an output section. The sealing section includes a seal bar having a heat pipe and the heat pipe has a means for relieving pressure within the heat pipe when the pressure substantially exceeds a desired level.
According to a fifth aspect of the invention a seal bar for a bag making machine has a surface that imparts a seal on a film, a heater, and at least one heat pipe disposed near the heater. The heat pipe has a relief zone on the at least one heat pipe.
According to a sixth aspect of the invention a method of preventing excess pressure in a heat pipe, such as that for a bag machine, includes relieving the pressure in the heat pipe through a relief zone when the pressure substantially exceeds a desired level.
According to a seventh aspect of the invention a heat pipe, such as that for bag making machine, is a pipe with a means for venting pressure when the pressure in the heat pipe near the means for venting substantially exceeds a desired level.
The relief zone includes a valve that opens to relieve pressure, that can be closed and reopened, or the relief zone can be a destructive relief zone in various embodiments.
The heat pipe is a generally closed cylindrical shape with the relief zone located on one end in another embodiment.
The heat pipe can have a second relief zone, possibly located at the other end of the heat pipe in another embodiment.
Fluid is in the heat pipe in another embodiment.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.
Before explaining at least one embodiment of the invention in detail it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. Like reference numerals are used to indicate like components.
While the present invention will be illustrated with reference to a drum based bag making machine, using certain components, it should be understood at the outset that the invention may be implemented on other machines, such as shuttle machines, pouch machines, etc., and using other components. Also the invention may be a seal bar with a heat pipe and without the bag machine, or simply a heat pipe and without the seal bar or bag machine.
The invention may be implemented using a bag machine such as that shown in
Generally, the invention includes a heat pipe that relieves pressure to prevent a catastrophic failure. The preferred embodiment provides that the pressure relief is provided through a relief zone. Relief zone, as used herein, includes an area or areas of a heat pipe through which an undesired excess pressure may be relieved, vented, reduced, or discharged. Various embodiments provide for a destructive relief zone, or a reusable relief zone, such as a valve. Destructive relief zone, as used herein, includes a relief zone wherein when the relief zone relieves pressure a portion of the relief zone is destroyed.
When a destructive relief zone is used, it is generally a one-time use, and the heat pipe is rendered unusable and must be replaced or repaired. For example, a destructive relief zone can be a solder plug that melts at a temperature less than the material that comprises the heat pipe, or a thinned wall that bursts before the entire heat pipe catastrophically fails. In either case the relief is controlled to reduce the likelihood of an uncontrolled explosion. The relief may be based on temperature, pressure, or a combination of pressure and temperature.
Referring now to
Heat pipe 304 can be similar (except for the relief zone) to a prior art heat pipe commercially available from CMD Corp. as part number 106131, which is a 0.375 inch diameter pipe, 60.00 inches long. However, in accordance with the preferred embodiment, relief zone 306 is provided and is provided with a relief zone 306. One alternative provides for a second relief zone 308.
Relief zone 306 is, in the preferred embodiment, a solder plug located at the end of heat pipe 300. The solder preferably has a melting range of 565-574 F, such as a solder comprised of 93.5% lead, 5% tin, and 1.5% silver.
When the temperature rises, and the pressure increases, the solder melts, and the pressure is relieved through the opening at the end of the heat pipe. Because the temperature melts the solder over a range, the temperature or pressure at the relief zone substantially exceeds threshold. Substantially exceeding a pressure, as used herein, includes the pressure being greater that a given value over a region for greater than an instantaneous period of time. The melting is caused by the high temperature, but it is load related to pressure in a closed system. Pressure in a closed system, such as heat pipe, is proportional to temperature, and therefore the use of pressure and temperature herein, is interchangeable when used herein, including the claims, to describe attributes of a closed system.
Alternative embodiments provide for relief zone 306 being a weakened wall or a valve, and/or relief zone 306 being located elsewhere, and/or additional relief zones. Relief zone 308, can likewise be a weakened wall, valve, and/or located elsewhere. Another alternative provides for heat pipe 304 to be located outside and adjacent seal bar 300.
Numerous modifications may be made to the present invention which still fall within the intended scope hereof. Thus, it should be apparent that there has been provided in accordance with the present invention a method and apparatus for a heat pipe and bag machine that fully satisfies the objectives and advantages set forth above. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11347172 | Feb 2006 | US |
| Child | 12325053 | US |
