Abstract:
A radiant energy device for shrinking a thin film onto an open top of a container, the radiant energy device comprising: a source of power, to provide power to the radiant energy device; a plurality of fixed energy-emitting units, each of the units when energized being configured to emit radiant energy towards the shrinking film on said open top of the container; and a switching means, operatively connected between the source of power and each of the energy-emitting units, to independently activate at least two groups of the energy-emitting units; wherein, a first group of the energy-emitting units partially shrinks the thin film onto the container, and a second group finishes the shrinking.

Description:
FIELD OF THE INVENTION 
     This invention relates to the general field of radiating energy devices, and more particularly to a device that radiates energy to shrink a thin film. 
     BACKGROUND OF THE INVENTION 
     Presently in the fast food drink industry it is typical to serve a drink in a paper, plastic or other disposable cup topped with a preformed plastic lid. However, there are a number of problems associated with the use of these plastic lids including high cost, a bulky size leading to difficulties in storage and disposal, leakage, and non-hygienic handling. In order to overcome these problems various devices and methods have been proposed in which a cover is placed on an open-topped container and then heated to shrink it into sealing engagement with the top of such a container. 
     One approach is provided in U.S. Pat. No. 5,511,360 to Bakker. This patent teaches a housing to receive and position the disposable cup. A thin film cut in a generally circular shape is urged across the open top of the cup, with an edge portion draping over the periphery. A first radiant energy source directs radiant energy to this overhanging portion. There is an energy absorbing means to absorb the energy and communicate it to the overhanging portion, causing it to shrink and form a seal around the periphery of the open top of the cup. Subsequently a second radiant heater shrinks the top portion of the thin film, completing the seal. 
     The first radiant energy source taught in the patent comprises two or more heaters, preferably tungsten halogen lamps, that are mounted on pivot arms and connected by slip rings and other complicated mechanical links back to a drive belt and a dedicated motor. Each lamp is only capable of directing energy towards a small portion of the film. Accordingly, the lamps must be rotated about the open top to ensure a complete seal. Application of the first radiant energy therefore involves positioning the lamps closely adjacent to the draped over edge of the thin film, activating the motor to rotate the lamps, and activating the lamps themselves to emit heat energy. 
     While this method effectively delivers the radiant energy, it requires many extra components and involves many moving parts, adding to the expense and complexity of the equipment. Further, since only a portion of the shrink film is exposed by the rotating lamps at any given moment of the process, the lamps need time to expose the full periphery of the container. In the “fast food” industry, time in seconds or even fractions of seconds are important. Thus the extra time required to rotate the lamps, as well as the cost and complexity of the equipment needed to support and operate the lamps is a disadvantage. 
     SUMMARY OF THE INVENTION 
     What is required is a radiant energy device for shrinking a thin film which overcomes the problems associated with the current devices. 
     Most particularly, the device should be relatively simple and uncomplicated, and preferably have only a few or no moving parts to minimize overall cost and maintenance requirements. The device should perform the task of shrinking the thin film and completing the seal as quickly as possible to accommodate the productivity demands of the food service industry. 
     The device of the present invention accomplishes these ends by arranging a lamp or lamps in a fixed position about the open top of the container, rather than by rotating them in space. In one embodiment an array of single lamps are positioned around the periphery of the open top end of the container. A switching means is included to energize the lamps in a patterned sequence to reduce peak energy consumption. In another embodiment a single lamp combined with a directing means is used to direct the radiant energy from a fixed position. 
     Accordingly, there is provided a radiant energy device for shrinking a thin film onto an open top of a container, said radiant energy device comprising: 
     (a) a source of power, to provide power to said radiant energy device; 
     (b) a plurality of fixed energy-emitting units, each of said units when energized being configured to emit radiant energy towards said shrinking film on said open top of said container; and 
     (c) a switching means, operatively connected between said source of power and each of said energy-emitting units, to independently activate at least two groups of said energy-emitting units; 
     wherein, a first group of said energy-emitting units partially shrinks said thin film onto said container, and a second group finishes said shrinking. 
     In a further embodiment there is also provided a radiant energy device for shrinking a thin film onto an open top of a container, said radiant energy device comprising: 
     (a) a source of power, to provide power to said radiant energy device; 
     (b) an energy-emitting body, said body emitting radiant energy upon being energized by said source of power; and 
     (c) a directing means defining an opening, said directing means being sized and shaped to direct said emitted radiant energy continuously about a periphery of said opening; 
     wherein, upon said energy-emitting body being energized, said directed radiant energy shrinks said thin film to cover said open top of said container. 
     In a further embodiment there is also provided a radiant energy device for activating a shrinking thin film to cover an open top of a container, comprising: 
     (a) a variable source of power, to provide power to said radiant energy source; 
     (b) a plurality of energy-emitting units, each of said units being configured to emit enough radiant energy towards said open top of said container at a high power level to cause said film to shrink, and to emit a low enough amount of radiant energy at a low power level to not cause said film to shrink; and 
     (c) a switching means, operatively connected between said source of power and each of said energy-emitting units, to switch said source of power between said high power level and said lower power level; 
     wherein, upon switching from said low power level to said high power level causes less of a power surge than switching said power level from off to said high level. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference will now be made, by way of example only, to preferred embodiments of the invention as illustrated in the attached figures. 
     FIG. 1 is a top view of the radiant energy device for shrinking a thin film of the present invention, where the energy device is an array of lamps; 
     FIG. 2 is a cross-sectional view of the radiant energy device of FIG. 1, showing the container and shrink film covering the container; 
     FIG. 3 is a front view of another embodiment of the radiant energy device of the present invention, where the device is a single lamp and the view is at the input ends of the lamp; 
     FIG. 4 is a top view of another embodiment of the radiant energy device of the present invention, where the device is a single lamp; and 
     FIG. 5 is a cross-sectional view of the single lamp embodiments of FIGS. 3 and 4, further showing the container, the shrink film covering the container, and a reflection coating inside the lamp. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a radiant energy device  10  of the present invention in the form of a plurality of individual energy-emitting units or light-emitting lamps  12 . The lamps are maintained in a fixed position around the outer periphery of the open top of a container  14 . It can be appreciated that the fixed position of the array of lamps  12  define an aperture in space that permits the entry of the container  14 . The container  14  may be a paper or plastic cup of the type commonly used to dispense drinks in a restaurant, vending machine, or other food service environment. Each lamp  12  comprises a bulb  16  and a curved reflective surface or reflector such as a mirror  18  that directs radiant energy emitted by the bulb  16  towards the container  14 . A thin film  20  stretches across the open top of the container  14  and overhangs the outer edge of container  14 . The curved surface  18  is sized and shaped to distribute radiant energy across a segment of the thin film  20  to be sealed, and at least sufficiently to cause shrinkage where it impacts the thin film  20 . Preferably the radiant energy is evenly distributed across the target segment, but the invention will work as long as enough radiant energy is provided to shrink the thin film  20  within the desired time frame. 
     A switching means  22  is represented functionally as a controller operatively connected to each of the lamps  12 . Each lamp is designated as a member of a group of lamps “A” or “B”. It can be appreciated that a control wire  24  from switching means  22  is operatively connected to each of the designated “A” lamps, while a control wire  26  is similarly connected to each of the designated “B” lamps. The switching means  22  is preferably implemented as part of an electronic control circuit that is generally an element of the broader lid-forming device. A source of power  27  supplies power to the radiant energy device  10  of the present invention. When power is provided to an energy-emitting unit, the unit is energized and emits radiant energy towards the thin film  20 , causing the targeted portion of film to shrink. 
     FIG. 2 shows the same device  10  of FIG. 1 in a side cross-sectional view. In this view the thin film  20  and the overhang over the edge of the container  14  may be more clearly seen. Two of the lamps  12  are shown connected through control wire  24  to controller  22 . Also shown is a support structure  28  associated with the broader lid-forming device, such as the one described in U.S. Pat. No. 5,511,360 to Bakker. In this figure the thin film  20  is shown just before it is to be shrunk around the rim of the container  14 . 
     Each of the energy-emitting units or lamps  12  is in approximately the same position in space relative to the rim of the container  14  as each rotating first radiant energy source was in the Bakker patent described above. The units  12  are also preferably tungsten halogen lamps in the range of 200-300 watts, though it can be appreciated that other energy-emitting units which produce sufficient radiant energy may also be used. In particular, it can be appreciated that such energy-emitting units may also be used as long as the thin film  20  is sensitive to and shrinks in response to the particular type or frequency of radiation energy emitted. 
     A plurality of eight lamps  12  are shown in FIG. 1 as that number has provided adequate results. It can be appreciated that a plurality of 4, 6, or more than 8 lamps  12  may also be feasible. An even number of lamps  12  is convenient to accommodate switching between at least two groups, as discussed below, but is not a requirement and an odd number of lamps  12  may also be used. 
     Since the lamps  12  of the present invention are fixed in position rather than rotating as in the prior art, there will generally be a greater concentration of energy adjacent to the container  14 . Further, the edge of the thin film  20  around the periphery of container  14  may be exposed to varying amounts of radiation depending upon how close a portion is to a lamp  12 . However, it is a general characteristic of the shrinking-type thin film  20  that it will shrink up to a designated percentage amount, typically about 50%. Accordingly, the risk of any portion of the thin film  20  “overshrinking” from exposure to a nominally greater amount of radiation is measurably reduced. 
     The present invention comprehends activating only a portion of the plurality of lamps  12  at one time, to ensure that peak consumption of power drawn from the power source  27  does not exceed an optimum value. Generally the optimum value is 15 amps at 110 volts, though it can be appreciated that other optimum power levels may be desired, for which individual lamp power values may be adjusted accordingly. For example, in FIG. 1 the designated “A” lamps may be turned on for ½ second and turned off, whereupon the designated “B” lamps will immediately follow for ½ second. The switching means  22  is operatively connected between the source of power  27  and the energy-emitting units  12 , and controls the switching between groups of lamps  12  and the on/off activation time period. The switching means  22  thereby independently activates each of the groups of lamps. 
     It can be appreciated that by energizing the array of lamps  12  in a patterned sequence, a plurality of lamps  12  fixed in position can be used in this application without exceeding the peak power consumption demanded by the rotating lamps of the prior art. 
     Peak power consumption is significantly influenced by the instantaneous turning on and off of the lamps  12 . Accordingly, another means of energizing the array of lamps  12  of the present invention involves maintaining a constant low power output or current level, or trickle of current, through all of the lamps  12 , and then fully energizing all of the lamps  12  simultaneously with a high power level when it is desired to shrink the thin film  20 . The power source  27  would accordingly provide variable power levels. The low current level would be selected to be sufficiently low so as not to cause any shrinkage of thin film  20 . Since in this embodiment the full power would be reached starting from a low level of current rather than zero current, the peak power demand or surge would be measurably reduced in comparison with energizing all of the lamps  12  from an off or zero power level. Accordingly, in this embodiment the switching means  22  would switch all of the lamps  12  from a low power level to a full power level. The lamps  12  would not need to be designated into discrete groups, and all of the lamps  12  could be controlled from a single control wire. 
     FIGS. 3,  4 , and  5  show a second embodiment of the present invention. In this embodiment a single fixed radiant energy-emitting body such as a light-emitting lamp  12  is used to emit radiant energy upon being energized by the power source  27 . The energy-emitting body or lamp  12  may be sized and shaped to have an opening that surrounds the outer periphery or rim of the open top of container  14 , and is accordingly generally annular in shape. In that case, the energy-emitting body will emit radiant energy continuously about a periphery of the opening. 
     There is also a directing means  30  to direct and concentrate the emitted radiant energy continuously about the perimeter of the open top of the container  14 . The directing means  30  is most commonly in the form of a reflective device, and defines an opening in which the container  14  is positioned. The directing means  30  is sized and shaped to direct the emitted radiant energy continuously about a periphery of the opening. This may include, for example, directing the emitted radiant energy inwardly, towards the opening. In this way the radiant energy may be directed to the portion of thin film  20  overhanging the rim of the container  14 . 
     The lamp  12  is preferably a tubular quartz halogen lamp, of the type commonly employed for cookers, range top heaters and the like. An example of this type of commercially available lamp is made by Philips Electronics, Part No. 16701R-FB. However, an aspect of this embodiment of the invention is that the single lamp  12  needs to completely surround the container  14  to effectively seal the entire periphery. At the same time, provision must be made for input leads  32  to provide power from power source  27  to the lamp  12 . In many commercially available lamps, such as the Philips model described, there is a spot on the point where input leads  32  enter the quartz envelope that has no filament and hence no radiation output. Accordingly, the design of the lamp  12  must accommodate the input leads  32  without imposing a gap in the continuous path of emitted radiation around the periphery of container  14 . 
     FIG. 3 shows one design of the lamp  12  of the second embodiment of the present invention, the lamp having input leads  32 . Electrical power to input leads  32  is turned on and the lamp  12  is energized when the container  14  and thin film  20  enter inside the annular configuration of the lamp. In this figure the lamp  12  is sized and shaped so that the input leads  32  overlap to avoid a gap in emitted radiation. The emitted radiant energy is accordingly continuous about a periphery of the opening defined by the lamp  12  and directing means  30 . As can be seen, the portion of the lamp  12  closest to the input leads  32  is offset on either side from the plane of the rest of the lamp  12  to accommodate the overlap. It has been found that the radiation emitted by the offset portion is adequate to seal the corresponding portion of the thin film  20 . If desired, the directing means or reflective device  30  may be oriented to better direct and concentrate the emitted radiation emanating from the offset portion. 
     In FIG. 4 a more conventional lamp such as the Philips model is used, and a second energy-emitting body or halogen bulb  34  is placed in the gap created by the input leads  32 . The energy output of bulb  34  is selected to blend in with the overall continuity of radiation, so that the radiation emitted in the gap is approximately the same as that which would be produced in the same space by the larger lamp  12 . The emitted radiant energy is accordingly continuous about a periphery of the opening defined by the lamp  12  and directing means  30 . 
     FIG. 5 is a view of this embodiment of the invention in cross section, showing the lamp  12 , container  14 , and thin film  20 . FIG. 5 also shows the directing means  30  in the form of a reflective coating of a portion of the lamp  12 . The coating of the lamp  12  may be either on the inside or on the outside of the glass on the outside perimeter of the lamp  12 , creating a shape that can effectively and efficiently reflect the radiant energy inward, towards the container  14 . Alternatively, the directing means  30  may be a traditional reflective device such as a separate reflective curved shaped mirror around the exterior of the lamp  12 . It has been found that a reflective surface formed of gold has provided adequate results, but it can be appreciated that other reflective materials may also be used as long as they efficiently reflect the emitted radiation. 
     It can be appreciated that, as with the first embodiment, the lamp  12  is in approximately the same position in space relative to the rim of the container  14  as each rotating first radiant energy source was in the Bakker patent described above. The power of the single lamp  12  is preferably in the range of 750-1000 watts, though other power levels that provide adequate results may also be used. In the configuration of FIG. 4, it has been found that for a lamp  12  rated at 1000 watts a bulb 34 of 100 watts provides adequate results. 
     It can be appreciated that the fixed position of the radiant energy device of the present invention provides an effective means of sealing the open top of a container with, for example, an energy absorbing shrinking thin film, without the expensive and complex equipment required to rotate lamps shown in the prior art. Further, as there are no moving parts and the process is governed by electrical processes and instantly-on halogen lamps, the time required to complete the seal is measurably reduced. As noted, an improvement in speed is a desirable feature in the food service industry. 
     Yet another benefit of the present invention is that it allows the overall lid-forming device to effectively shrink a rectangular segment or cut piece of thin film around the container rim. This is an advantage in that a piece of thin film may now be cut directly off a roll of thin film and placed on the container without having to be cut in a circular fashion, as required in the prior art. Where an array of lamps are used, the corners of the rectangular thin film can be presented directly adjacent to four of the lamps so that the extra film of the corners can be neatly shrunk, substantially out of sight, around or even under the rim. 
     It will be appreciated by those skilled in the art that the foregoing description was in respect of preferred embodiments and that various alterations and modifications are possible within the broad scope of the appended claims without departing from the spirit of the invention. For example, with respect to the first embodiment of the invention, while division of the array of lamps into two switched groups has provided adequate results it can be appreciated that three or more groups may also be feasible. Various other modifications will be apparent to those skilled in the art but are not described in any further detail herein.