Abstract:
A laminating arrangement comprising: a laminating roller; a radiating element adapted to radiate energy therefrom towards the laminating roller; a temperature detecting arrangement, adapted to detect the temperature at the surface of the laminating roller; and a processor adapted to receive a signal from the temperature detecting arrangement device and to control the intensity of radiation emitted by the radiating element, wherein: a maximum warm-up rate is defined; and during a warm-up phase of the laminating arrangement, the rate of increase in temperature at the surface of the laminating roller is determined by the processor, and the intensity of radiation emitted by the radiating element is increased if the rate of increase of temperature is less than the maximum warm-up rate, and is decreased if the rate of increase of temperature is greater than the maximum warm-up rate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a laminating device, and particularly concerns a laminating device which is able to warm up to its operating temperature within a relatively short space of time. 
         [0002]    Laminating devices are widely used for sealing items within translucent or transparent pouches, so that the items can be displayed and/or stored and remain protected from dirt, moisture and so on. 
         [0003]    One problem with most conventional laminating machines is that, when the machine is initially switched on, it takes a relatively long time before the machine is ready to perform a laminating operation. This is because the rollers of the machine must be heated up to a high temperature. In conventional laminating machines, each roller is partially surrounded by a heavy “shoe” formed from a material such as aluminium. The shoes are heated, typically by resistance heating, and heat energy is transferred from the shoes to the rollers by radiation and convection. 
         [0004]    Whilst shoes of this type have proved to be effective at maintaining the rollers at the desired operating temperature, it will be appreciated that laminating machines using this technique will take a considerable length of time for the rollers to reach a suitable laminating temperature. 
         [0005]    More recently, it has been proposed to heat the rollers by directing radiation from halogen bulbs onto the surfaces of the rollers. The heat produced by halogen bulbs is, however, intense, and it has proved difficult to heat rollers consistently and reliably in this manner. It has also been found that, if the surfaces of the rollers (which are typically formed silicone) are overheated, they may become permanently damaged, which may render the entire machine inoperable. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an objective of the present invention to provide an improved laminating device. 
         [0007]    Accordingly, one aspect of the present invention provides a laminating arrangement comprising: a laminating roller; a radiating element adapted to radiate energy therefrom towards the laminating roller; a temperature detecting arrangement, adapted to detect the temperature at the surface of the laminating roller; and a processor adapted to receive a signal from the temperature detecting arrangement and to control the intensity of radiation emitted by the radiating element, wherein: a maximum warm-up rate is defined; and during a warm-up phase of the laminating arrangement, the rate of increase in temperature at the surface of the laminating roller is determined by the processor, and the intensity of radiation emitted by the radiating element is increased if the rate of increase of temperature is less than the maximum warm-up rate, and is decreased if the rate of increase of temperature is greater than the maximum warm-up rate. 
         [0008]    Conveniently, an operating temperature is defined, being the temperature at which the laminating roller is to be maintained during laminating operations, and a maximum temperature is also defined, wherein, during the warm-up phase, the temperature of the laminating roller is increased to the maximum temperature, and wherein the maximum temperature is at least 25° C. higher than the operating temperature. 
         [0009]    Advantageously, the maximum temperature is at least 30° higher than the operating temperature. 
         [0010]    Preferably, the maximum temperature is at least 35° higher than the operating temperature. 
         [0011]    Conveniently, a lag time is defined, and wherein, following a change in intensity of radiation emitted by the radiating element, no further change in intensity may occur until the lag time has expired. 
         [0012]    Advantageously, the lag time is at least substantially as long as the time taken for the laminating roller to complete a revolution at a rate of rotation used during laminating operations. 
         [0013]    Preferably, the lag time is less than approximately the time taken for the laminating roller to form two complete revolutions at the rotation rate employed during laminating operations. 
         [0014]    Advantageously, the laminating roller is rotated whenever the radiating element is activated. 
         [0015]    Conveniently, during an operation phase of the laminating arrangement, which follows the warm-up phase, the intensity of energy radiated from the radiating element is controlled, in accordance with the detected temperature of the surface of the laminating roller, to maintain the surface of the laminating roller at or near an operating temperature thereof. 
         [0016]    Preferably, a plurality of high temperature bands are defined above the operating temperature, and the intensity of radiation emitted by the radiating element is controlled in dependence of the high temperature band in which the detected temperature of the surface of the laminating roller falls. 
         [0017]    Advantageously, one or more low-temperature bands are defined below the operating temperature and wherein the intensity of the radiation emitted by the radiating element is controlled in accordance with the low temperature band in which the detected temperature of the surface of the laminating rollers falls. 
         [0018]    Conveniently, one or more fans are provided, the fans being positioned to direct a stream of air across a surface of the laminating roller to cool the laminating roller. 
         [0019]    Advantageously, the rate of rotation of the one or more fans is controlled in accordance with the detected temperature at the surface of the laminating roller. 
         [0020]    Preferably, the laminating arrangement is configured so that, after passing over the surface of the laminating roller, air blown by the one or more fans is directed towards an exit point of the laminating roller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    In order that the present invention may be more readily understood, embodiments thereof will now be described, by way of example, in which: 
           [0022]      FIG. 1  is a schematic view of components of a laminating machine, of the type that may be used for the present invention; 
           [0023]      FIG. 2  shows a graph of the temperature of the surface of one of the rollers of the machine of  FIG. 1  during warm up and subsequent laminating operations; and 
           [0024]      FIG. 3  is a view of further components of a laminating machine that may be used for the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Turning firstly to  FIG. 1 , some of the internal components of a laminating machine embodying the present invention are shown. The laminating machine includes a pair of rollers  1 , 2 . Each roller comprises a solid core  3 , made from a material such as steel, with a relatively thin silicone covering  4  being formed around the core  3 . The thickness of the silicone covering  4  with respect to the core  3  is exaggerated in  FIG. 1  for the purposes of clarity. 
         [0026]    The rollers  1 , 2  are parallel with one another, and are preferably biased into contact with one another by means of a spring-loaded element (not shown). The rollers  1 , 2  are rotatable around respective spindles  5 , and may be driven to rotate in opposite directions by a gearing system (not shown) which is in turn connected to a drive motor. With reference to  FIG. 1 , the upper roller  1  will be driven in an anti-clockwise direction, and the lower roller  2  will be driven in a clockwise direction, so that items to be laminated may be drawn between the rollers  1 , 2  from left to right. Respective halogen lamps  6  are provided to radiate heat energy to the upper and lower rollers  1 , 2 . Each halogen lamp  6  comprises an elongate halogen bulb  7 . In preferred embodiments of the invention, the halogen bulbs  7  are approximately the same length as the rollers  1 , 2 , and are arranged to be substantially parallel therewith. 
         [0027]    A reflector  8  is provided around each halogen bulb  7 . The reflectors  8  are formed from a reflective material, such as aluminium. Each reflector  8  is preferably arranged so that radiation emitted from the halogen bulb  7  is reflected from the internal surfaces of the reflector  9 , and is concentrated so as to exit the reflector  8  in a particular direction. With reference to  FIG. 1 , the reflector  8  that is provided around the halogen bulb  7  that is provided to heat the upper roller  1  is arranged so that radiated energy is reflected to leave the reflector  8  in a direction directly towards the upper roller  1 , as indicated by the arrow  9 . Similarly, the reflector  8  provided around the halogen bulb  7  that is arranged to heat the lower roller  2  concentrates radiated energy and directs it towards the lower roller  2 , as indicated by the arrows  10 . 
         [0028]    It will be understood that at least a part of the cross-section of each reflector  8  may be parabolic. Preferably, each reflector  8  is also elongate, is approximately the same length as the halogen bulb  7 , and is arranged to be parallel with the halogen bulb  7 , having a substantially consistent cross-sectional shape along its length. Each reflector  8  is therefore generally trough-shaped. 
         [0029]    The components as illustrated in  FIG. 1  are arranged to heat the rollers from ambient temperature to operational temperature in the shortest possible time. For this reason, powerful halogen bulbs  7  are provided, and the halogen bulbs  7  are provided relatively close to the surfaces of the rollers  1 , 2 —in preferred embodiments of the invention, the distance between each bulb  7  and the respective roller is between 4 mm and 10 mm. 
         [0030]    The halogen bulbs  7  may have power ratings up to several hundred watts. For instance, an A3-size laminating device will require a 600 w bulb in order to heat the rollers  1 ,  2  to the required operating temperature in less than one minute. An A4 laminating device will require a 400 w bulb to warm up in this time. These values are approximate, however. 
         [0031]    As discussed above, if the silicone material that forms the outer surfaces  4  of the rollers  1 , 2  is heated above a certain temperature it may be permanently damaged. It is, therefore, important that such overheating does not occur. 
         [0032]    The temperature of the surface of each roller  1 , 2  is monitored by a temperature detecting arrangement  15  (shown schematically in  FIG. 1 ) In preferred embodiments, the temperature of the surfaces of the rollers  1 , 2  may be measured directly by any suitable means, for instance by one or more bimetallic strips placed at or on the surface of each roller  1 , 2 . The output from the temperature detecting arrangement  15  is fed to a processor  16  of the laminating machine. The processor  16  is also operable to control the operation of the halogen bulbs  7 , by varying the power supply to the halogen bulbs  7 , or by turning the halogen bulbs  7  off entirely. 
         [0033]    The operation of the laminating machine will now be described, when the laminating machine is first switched on. The rollers  1 , 2  are, initially, substantially at the ambient temperature of the surroundings. The halogen bulbs  7  are switched on, and radiation from the bulbs  7  is directed towards the surfaces of the rollers  1 , 2 . 
         [0034]    Stored in a memory that is accessible by the processor  16  is a maximum warm-up rate for the rollers  1 , 2 . This rate represents the fastest rate at which power, in the form of heat energy, may be delivered to the surfaces of the rollers  1 , 2  by halogen bulbs  7  of the type used in the laminating machine, without incurring a significant risk of damage to the surfaces of the rollers  1 , 2 . As the surfaces of the rollers  1 , 2  warm up, the rate at which the temperatures of the roller surfaces increases is compared with the stored maximum warm-up rate. 
         [0035]    If the temperature of the surfaces of the rollers  1 , 2  is rising more slowly than the maximum warm-up rate then the intensity of the halogen bulbs  7  may be increased, although of course if the halogen bulbs  7  are already at their maximum intensity then further increase will not be possible. 
         [0036]    Conversely, if the temperature detecting arrangement  15  indicates that the temperature of the surfaces of the rollers  1 , 2  is rising at a rate which is greater than the maximum warm-up rate, the intensity of the halogen bulbs  7  may be decreased. 
         [0037]    It will be understood that the rate at which the temperature of the surfaces of the rollers  1 , 2  warms up will not be entirely predictable. Factors such as the ambient temperature, manufacturing tolerances in the production of the halogen bulbs, and variations in the local power supply, will dictate that the warm-up rate cannot be determined simply by defining a pre-set intensity of the halogen bulbs  7 . 
         [0038]    Referring to  FIG. 2 , a graph of temperature with respect to time is shown, following switching on of the laminating machine. During a warm-up period W, the temperature  11  of the surfaces of the rollers  1 , 2  rises, and is maintained as close as possible to the maximum warm-up rate  12  by the feedback arrangement described above. 
         [0039]    A maximum temperature T max  is defined, and when the temperature of the surfaces of rollers  1 , 2  reaches the maximum temperature, the warm-up phase W is complete. At this point, the laminator is ready to perform a first laminating operation, and an outward indication of this is preferably provided, for instance the switching on of a green “ready” lamp on an exterior of the laminating machine. 
         [0040]    It is anticipated that, using the above technique, a roller may be heated to the maximum temperature T max  within around 30 seconds. Because the rollers have been heated up in a short space of time, the majority of the heat energy that has been transferred to the rollers  1 , 2  will be concentrated at the very outermost portions thereof, and heat energy will not have had time to be transmitted to inner portions of the coverings  4  of the rollers  1 , 2 . Therefore, when a first pouch to be laminated is passed between the rollers  1 , 2 , the temperature of the rollers  1 , 2  will drop sharply, as the heat energy concentrated at the very outer edges of the rollers  1 , 2  will be transmitted to the pouch. 
         [0041]    For this reason, the maximum temperature T max  is considerably higher than the intended operating temperature T op  of the laminating machine, with the intention being that, when the first pouch, or few pouches, pass between the rollers  1 , 2 , the temperature of the rollers  1 , 2  will drop to the operating temperature T op . 
         [0042]    In preferred embodiments of the invention, the operating temperature T op  is around 110° C. The maximum temperature T max  however, preferably set to be around 150° C. Referring again to  FIG. 2 , it can be seen that in an initial use period I, the temperature falls rapidly from the maximum temperature T max  to the operating temperature T op . 
         [0043]    In further embodiments of the invention, the maximum temperature T max  is at least 25° C. higher than the operating temperature T op . More preferably, the difference between these temperatures is at least 30° C., and still more preferably the difference between these temperatures is at least 35° C. 
         [0044]    Following the initial use period, the laminator will enter an operation period O, in which the operating temperature of the rollers  1 , 2  will be maintained for subsequent laminating operations. 
         [0045]    As discussed above, the use of powerful halogen bulbs  7  provided in close proximity to the surfaces of the rollers  1 , 2  will mean that large quantities of heat energy are transmitted to the rollers  1 , 2 . If overheating of the rollers  1 , 2  and hence permanent damage therefore, is to be avoided, it is necessary to control the heating of the rollers  1 , 2  carefully. 
         [0046]    One way in which this may be achieved is to ensure that there must be a minimum time lag between changes in the intensity of the energy supplied by the halogen bulbs  7 . For instance, the circumference of each roller may be around 20 cm, and the throughput rate of the laminating device may be around 300 cm per minute. This means that each roller makes a complete revolution in approximately 4 seconds, and the processor  16  of the laminating machine may therefore be set so that, following a change in intensity of the radiation delivered by the halogen bulbs  7 , and further changes in the intensity may be applied for a period of at least 4 seconds. This will help to ensure that localised “hot spots” on the surfaces of the rollers  1 , 2  do not occur. 
         [0047]    In preferred embodiments, the time lag following a change of bulb intensity during which no further changes in intensity may be made is at least the time taken for one complete revolution of one of the rollers  1 , 2 . The time lag may be set to be longer than this, but is preferably not longer than the time taken for two complete revolutions of one of the rollers  1 , 2 . 
         [0048]    Referring again to  FIG. 3 , the machine may also include one or more fans  13 , which are arranged to blow air over the surfaces of the rollers  1 , 2 , thereby cooling the surfaces. The one or more fans  13  may be activated when the temperature of the surfaces of the rollers  1 , 2  exceeds the target operating temperature by a predetermined amount. 
         [0049]    It is anticipated that, in certain embodiments of the invention, the lowest intensity of radiation may be supplied by each of the halogen bulbs  7  (short of the halogen bulbs  7  being switched off) will be sufficiently high that, if there is a long gap between laminating operations, the surfaces of the rollers  1 , 2  may overheat. During the times between laminating operations, therefore, the fans  13  may be activated to trim excess heat from the rollers  1 , 2 , and this may occur while the halogen bulbs  7  are still switched on. 
         [0050]    During the operation period O of the laminating machine, feedback from the temperature detecting arrangement will preferably continue to be used to control the intensity of radiation provided by the halogen bulbs  7 . In preferred embodiments, a look-up table will be used to control the bulb intensity. For instance, if the operating temperature T op  is 110°, a first high temperature band H 1  may be defined between 110° and 115°. A nominal bulb intensity is defined, which is expected to maintain the surfaces of the rollers  1 , 2  at the operating temperature during normal operation. If the temperature of the surfaces of the rollers  1 , 2  is detected to be within the first high temperature band H 1 , however, then the intensity of the bulbs  7  may be reduced by a preset amount, for instance to 70% of the nominal intensity. Preferably, a second high temperature band H 2  is defined between 115° or 120°, and a further reduction intensity may be defined with respect to this band. Further high temperature bands may also be defined. 
         [0051]    Similarly, low temperature bands may be defined. A first low temperature band H 1  may be set to be between 105° and 110°, and if the detected temperature falls within this band H 1  then the intensity of the bulbs  7  may be increased to 130% of the nominal intensity. 
         [0052]    The widths of the bands, and the bulb intensities associates with these bands, are not limited to those described above, and may be set during a calibration process to any suitable values. 
         [0053]    It is also anticipated that the operation of the fans  13 , if these fans  13  are provided, may be such that the fans  13  are activated if the detected temperature of the surfaces of the rollers  1 , 2  falls within the temperature bands. These temperature bands may correspond to those defined for the bulb intensity, or alternatively may be defined separately. Preferably, the fans  13  may be operated to rotate at varying rates, and it will be understood that the fans  13  may be operated to rotate at a higher rate if the detected temperature of the rollers  1 , 2  falls within a higher band. 
         [0054]    In preferred embodiments of the invention, the fans  13  and other components of the laminating machine are configured so that air blown by the fans  13  is directed, after passing over the surface of one of the laminating rollers  1 , 2 , towards an exit point of the laminating rollers  1 , 2 . For instance, the shape of internal surfaces (not shown) of the housing  14  of the laminator may be angled so that, once air blown by the fans  13  is passed over the surface of one of the rollers  1 , 2 , the air is deflected by this internal surfaces towards the exit point of the rollers  1 , 2 . 
         [0055]    A schematic view of the flow of air in these embodiments is shown in  FIG. 3 . 
         [0056]    As discussed above, due to the intensity of the halogen bulb  7  it is possible that, more particularly during the first few laminating operations after the machine has switched on, laminated pouches exiting the rollers  1 , 2  may be heated to a very high temperature. A directing of air from the fans  13  towards the exit point of the rollers  1 , 2  will help to cool these pouches, which will help prevent distortion of the pouches, and also help to ensure that the pouches are at a reasonable temperature to be grasped by a user as they exit the laminating machine. 
         [0057]    In variations of the invention, the laminating machine may be included to warm up in a longer time period, for instance around one minute. In these embodiments, some of the measures described above may not be necessary. For instance, if the laminating device is configured to warm up in around one minute, it is anticipated that the “overshooting” of the temperature to a maximum temperature which is significantly above the operating temperature may not be necessary. Also, it is anticipated that it will not be necessary to place the halogen bulbs so close to the rollers  1 , 2 , and therefore the provision of fans may be unnecessary. 
         [0058]    It will be understood that embodiments of the present invention may provide laminating machines which warm up in a considerable shorter time than is presently practically possible. 
         [0059]    When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.