FR2499457A1 - DEVICE FOR RECOVERING THE SURFACE OF A SHEET - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS A DEVICE FOR COVERING THE SURFACE OF A SHEET. ACCORDING TO THE INVENTION, IT INCLUDES TWO ROLLERS 1A, 1B FORMING A PINCH ROLLER 4 FOR TRANSPORTING A SHEET 2 OF WHICH AT LEAST ONE SURFACE IS COVERED WITH A PLASTIC FILM 3, A LAMP 7A OR 7B IRRADIATING THE HEAT ARRANGED TO FACING THE EXTERNAL CIRCUMFERENCE OF AT LEAST ONE OF THE ROLLS WHEN BUTTING ON THE PLASTIC FILM; AND A 10 PHASE CONTROL CIRCUIT TO CONTROL THE ELECTRICAL CURRENT THAT SHOULD BE APPLIED TO THE LAMP; THE PHASE CONTROL CIRCUIT CONSISTS OF A TRIAC CONNECTED IN SERIES WITH THE LAMP, A TEMPERATURE SENSOR ON THE EXTERNAL CIRCUMFERENCE OF THE ROLLER HEATED BY THE LAMP, AND A CIRCUIT FOR MONITORING THE DRIVING TIME OF THE TRIAC ACCORDING TO THE SIGNAL FROM THE DETECTOR TEMPERATURE. THE INVENTION APPLIES IN PARTICULAR TO THE COLLECTION OF BUSINESS CARDS, IDENTITY CARDS, SEASONAL CARDS, MINIATURE CALENDAR AND OTHERS.

Description

The present invention relates to a device for covering very

  precisely the surface of a sheet such as a card or a label by means of a plastic film. More particularly, the present invention relates to a device of the above type, which is enabled to accomplish a stable covering operation by using at least one heat irradiation lamp as a heat source and

  controlling the phase of the current to be applied to this lamp.

  In a sheet such as a "business card", an "identity card", a "seasonal card", a "miniature calendar" or other cards or labels, in general, it is convenient or frequently necessary to form a card. surface covering, which may be a mode of packaging, so as to impart, to this sheet, durable properties and impermeability, to improve or prevent the items indicated on the sheet to be modified. As a result of this need, a wide variety of devices for covering the surface of a

  sheet have been proposed according to the prior art.

  Fig. 1 is an explanatory view showing an essential part of an example of a prior art sheet-surface covering device. This device covers both surfaces of the sheet and is constructed so that two hollow rollers 1A and 1B are arranged in abutting mode

  in a passage P of the sheet, where a sheet 2

  placed in or sandwiched between a folded plastic covering film 3, is transferred to move, thereby to build a nip roll 4, heaters 5A and 5B being arranged in the respective internal spaces 11A and 11B

  rollers 1A and 1B above mentioned.

  The above-mentioned plastic covering film 3 is prepared, as shown in FIG. 2 by way of example, by applying an adhesive layer AL made of a thermoplastic resin such as polyethylene, on one face of a surface layer CL made of a polyester film or the like, thereby forming a film member by sealing the two film bodies thus formed by a side E so that the adhesive layers AL are internally

turned towards each other.

  In the device for covering the surface of a sheet having the construction which has just been described, the rollers 1A and 1B mentioned above are

  heated from the inside by the heaters 5A and 5B

  mentioned above, and the sheet 2 sandwiched between the plastic film 3 is transferred along its passage P until the aforementioned plastic film 3 is heated and pressed to the region of S abutment, where the rollers 1A and 1B above abut one another, by the cooperation of the rollers 1A and 1B so that it is welded to the sheet 2 above, for

  thus cover the two surfaces of the sheet 2.

  Moreover, in a device for covering a surface of a sheet, one of the heaters 5A or 5B

may be omitted, as the case may be.

  Nevertheless, so that the recovery device

  the surface of a leaf thus described may

  squeeze and cover the surface (s) of the sheet 2

  to be covered7 even if this sheet has different thicknesses

  In those embodiments, the rollers 1A and 1B described above are formed sufficiently thick to have a high heat capacity. Consequently, in the case where the device under consideration must operate with its respective rollers which are

  left in their cold state after a relative interruption

  For example, it is a long time since the above-mentioned heaters 5A and 5B are supplied with electric power so that their operation begins until the temperatures on the external circumferences are reached. respective rollers 1A and 1B above reach a level sufficient to obtain the

  desired surface overlays.

  Therefore, the device according to the prior art has the disadvantage of having a long warm-up time. The present invention therefore relates to a device for covering the surface of a sheet which has a short time of heating, while being freed from the disadvantages described above, and which makes it possible to

  stabilize the heating temperature.

  Another object of the present invention is a device for covering the surface of a sheet having a short preparation time prior to use, and which can maintain the temperature at the abutting region between the rolls at a constant level.

desired, without fault ..

  The invention will be better understood, and other purposes, features, details and advantages thereof

  will become clearer during the description

  following explanatory diagram with reference to the accompanying schematic drawings given solely by way of example illustrating several embodiments of the invention and in which: - Figure 1 is an explanatory view showing a device for covering the surface of the a sheet according to the prior art; - Figure 2 is a sectional view explaining the film of plastic covering; Figure 3 is a sectional view explaining an embodiment of the present invention; FIG. 4 is a circuit diagram showing an exemplary phase control circuit that may be used in the present invention; FIG. 5 is a diagram of a circuit showing another example of the phase control circuit that can be used in the present invention; and - Figure 6 is an explanatory view showing

  a concrete example of a temperature detector.

  Embodiments of the present invention will be described below with reference to Figs. 3 to 6 in the case of a construction for covering both surfaces of a sheet. In the embodiment shown in Fig. 3, the nip roll 4 is constructed from the pair of rollers 1A and 1B abutting each other in

  the passage P of the sheet, and concave mirrors reflecting

  6A and 6B, which are made of auiurium or the like and which are respectively open to face the passage P mentioned above of the sheet, are arranged to cover the regions of the outer circumferences of the respective rollers 1A and 1B to 1 exception of the region containing the abutment region S of rollers 1A

  and lB. In these reflecting mirrors 6A and 6B respectively

  Light-emitting lamps 7A and 7B are arranged such as halogen lamps or infrared lamps in order to cope with the irradiated outer edges HA and HB of the respective outer circumferences of the respective rollers 1A and 1B above, which are diametrically opposed to the abutment region S. The lamps 7A and 7B radiating heat thus arranged are cornectées to an AC power supply, made operative to provide electric current, by a circuit of

  phase control 10 for controlling the elec-

  of the AC power source.

  Thermal insulators 8A and 8B are mounted on the outer surfaces of the reflecting mirrors 6A and 6B

  above mentioned, respectively.

  The aforementioned phase control or control circuit 10 is formed (as can be seen in FIGS. 4 and 5) of a triac, which is connected in series with the aforementioned lamps 7A and 7B radiating the heat, a temperature detector 9 which is disposed in contact or near the roller 1B of the above set mentiomnné the pinch roll 4 so 249945i detect the temperature of the roll 1B and a control circuit CC used to control the production rate of triac tripping signal above

  in response to the signal from the temperature detector

  9. A temperature-sensitive resistive element

  whose resistance varies with temperature is of

  used extensively for the temperature detector 9

above mentioned.

  FIG. 4 shows a circuit diagram of an example of the control circuit or phase control in the case where a positive type thermistor PTC is used for the temperature detector 9. In this example, the phase control circuit is constructed so that it is connected to an AC power supply AC

  by a switch SW and by the irradiation lamps 7A and 7B

  which are connected in series or in

  parallel, a series connection consisting of the thermistor

  positive type PTC, a compensation resistor R1 and a capacitor C1 for controlling the conduction duration of the triac (hereinafter referred to as the "control capacitor") and so that a diode TD trigger is connected between the node between the

  control capacitor C1 and the compensating resistor

  R1 and trigger Trac triac G which is connected in series with the lamps 7A and 7B. The control capacitor C1, the compensation resistor R1 and the tripping diode TD together form the control circuit CC. Resistors R2 and R3 and a capacitor C2 are circuit elements for damping the hysteresis, and a resistor R4 and a capacitor C3 together form a current-absorbing circuit to prevent

  the malfunction of the TRC triac.

  According to the construction which has just been described, the outer circumferences of the respective rolls 1A and 1B are heated to the irradiated regions HA and HB, which are opposite the abutment region S, by the radiating heats emitted by the lamps 7A and 7B radiating heat. If, at this stage, Sheet 2 interposed in the

  plastic film 3 is forced into the

  1A and 1B of the entire nip roll 4, it is heated by the respective rollers 1A and 1B, while being clamped and carried by the heated nip roll 4, thus the adhesive layers AL of the plastic film 3 are softened to resume their adhesiveness until they are pressure welded to both surfaces of the sheet 2, so as to obtain the surface overlaps of this sheet 2. Furthermore, the functions of the irradiation lamps of 7A and 7B above are controlled by

  the control circuit or phase control 10, as follows.

  When the switch SW is closed, the control capacitor C1 is supplied and charged with the alternating voltage by the positive type PTC thermistor and the compensation resistor R1. When the charging voltage reaches the switching voltage of the trigger diode TD, the capacitor C1 in consideration discharges through the diode TD to apply the signal current to the gate of the triac TRC, so that triac TRC is made conductive for apply the electric currents to the lamps 7A and 7B radiating heat. The operations just described will be repeated for each half-period of

  the alternative voltage above. In this case, the temperature

  The above-mentioned positive type PTC thermistor depends on the temperature on the outer circumference of the roller 1B. Therefore, if this temperature,

  for example, is high and the resistance of the thermistor

  As the positive type PTC increases, the voltage to be applied to the capacitor C1 is lowered which lengthens the charging time before the charging voltage reaches the switching voltage of the trigger diode TD, and thus the conduction time of the triac. TRC at the half-period of the AC voltage is delayed. As a result, the currents flowing through the heat-radiating lamps 7A and 7B decrease according to the increase of 249945i.

  temperature of the PTC thermistor of the positive type

  above mentioned, and radiant heat emission

is accordingly diminished.

  If, on the contrary, the temperature on the circumference

  The external resistance of roller 1B is lowered and the PTC positive type thermistor has its resistance which decreases, the conduction time of triac TRC is advanced and the emission

  radiant heat by lamps 7A and 7B increases.

  According to the construction which has just been described, as the respective rollers 1A and 1B forming the nip roll 4 have external circumferences which are heated directly by the radiant heat and as irradiation lamps 7A and 7B, which can be switched on for If the predetermined radiating heat levels are used as heat sources for the respective rolls 1A and 1B, the temperatures on the outer circumferences of the respective rolls 1A and 1B can be raised to a level necessary to obtain the surface coating operations of the respective rolls 1A and 1B. a sheet in a remarkably short time from the moment the switch SW is closed to start the operations of the irradiation lamps 7A and 7B, even after a relatively long interruption of operations, that is to say even if the respective rolls 1A and 1B are

  started in their cold state, and therefore the heating time

  can be shortened. Moreover, as the temperature

  on the outer circumferences of the rollers 1A and 1B

  mentioned above is detected by the temperature sensor.

  9 and that the operations of the lamps 7A and 7B are controlled by the phase control circuit according to the signal of the temperature detector 9, the emission of light, that is to say the emission of radiant heat 7A and 7B lamps radiating heat varies, while the lamps 7A and 7B are actually lit at any time, according to the temperature variation on the outer circumferences of the rollers 1A and 1B. As a result, since there is no abrupt change in the temperature in the rollers 1A and 1B, contrary to the case of an all-or-nothing control, and the emission of heat

  radiant varies continuously and gently, the temperature

  the rollers IA and 1B can be maintained remarkably-

  stable at the desired level, and the surface coverings of the leaves can still be obtained stably and satisfactorily even if the apparatus is

  used continuously for a long period of time.

  Fig. 5 is an explanation view of another phase control circuit that can be used in the present invention. In this circuit, a negative type NTC thermistor is used as the temperature detector 9. More particularly, a rectifier RC is connected to the ac power source AC by the switch SW. To this rectifier RC is connected a clipping circuit which is formed, in combination, resistors R9 and R10 and zener odes ZDI and ZD2. To this clipping circuit is connected a series circuit formed of a resistor R7, a variable resistor VR8 and the NTC thermistor of the negative type. To this rectifier RC are also connected the control capacitor or control Cl by a resistor R5 and moon resistance

  variable VR6 and the NTC thermistor of the negative type

  above mentioned by a diode D1 in parallel with the

  capacitor Cl. In addition, to the clipping circuit

  above is connected by a resistor Rl 1, a base B2 of a unijunction transistor TUJT, the other base BI is connected to the primary coil of a pulse transformer PT. Cl capacitor mentioned above

  is connected to the emitter El of the UJT transistor above.

  The secondary coil of the pulse transformer PT is

  connected by a diode D1) to the gate G of the triac TRC.

  The control circuit CC is formed, for its major components, capacitor C1, resistors R5 and P7, variable resistors VR6 and VR8, diode D1,

  of the transistor UJT and the pulse transformer PT.

  Moreover, the marks C5 and D31 designate respectively 249945i

a capacitor and a diode.

  In the compound phase control circuit as above, the voltage from the clipping circuit is applied to the capacitor C1 by the resistor R7, the variable resistor VR8 and the diode D1, and by the resistor R5 and the variable resistor VR6 , depending on the resistance value of the NTC negative thermistor. The charges and discharges, the latter occurring when the charging voltage of the capacitor Cl exceeds the peak voltage of the emitter E 'of the transistor UJT and the first being performed again after the last, are repeated during the half-period of the alternating voltage. The pulse signals, forced to appear at the secondary coil of the pulse transformer PT by these charges and discharges, are applied by the diode D2 to the gate G of the triac TRC, which is made conductive by the first burst of these pulse signals. and is maintained in its conducting state during the half-period of the considered AC voltage. Moreover, the moment

  the first burst of the impulse signals

  above mentioned appears, depends on the voltage that must be applied to the capacitor Cl and as a result of the resistance of the NTC thermistor negative type, so the

  conduction time of triac TRC is controlled.

  Moreover, when the temperature on the cir-

  external conference of the roll 1B is raised to lower the resistance of the NTC thermistor of the negative type, the voltage to be applied to the capacitor C1 above is lowered and thus the conduction time of the triac TRC is delayed to reduce the emission of radiant heat lamps 7A and 7B. On the contrary, if the temperature on the outer circumference of the roll 1B is lowered, the resistance of the NTC thermistor of the negative type is high contrary to the above, and therefore the emission

  radiant heat of lamps 7A and 7B increases.

  By the phase control circuit which has just been described therefore, the lamps 7A and 7B are controlled under conditions where their radiant heat emission changes slowly with a small variation, which allows them to have the same effects as the lamps preceding. The electric current to be supplied to the above lamps 7A and 7B is controlled by the circuit 10 according to the signal coming from the temperature detector 9. However, as the rollers 1A and 1B mentioned above have a high heat capacity and as the Irradiation lamps 7A and 7B do not heat the rollers 1A and 1B as a whole, but consecutively the parts of the outer circumferences which are passed through the irradiated regions HA and HB by the rotations of the rollers 1A and 1B, there is reason to fear that the advantage of controlling the lamps 7A and 7B by means of the phase control circuit 10 is canceled in

  particular according to the position of the temperature detector 9.

  Therefore, in the present invention, the temperature detector 9 is disposed either in contact with or near the outer circumference of the roll 1B, as can be seen in FIG. 3, downstream of the abutment region S ci above the outer circumference of the roll 1B, that is to say in a position offset in rotation from the roll 11 and upstream of the irradiated region

above mentioned HB-

  According to the construction just described, as the temperature detector 9 above is arranged upstream of the irradiated region above HE, that is to say in a position which is offset in a manner opposite to the direction of rotation of the roller 1B considered, the outer circumference portion of the roller 1B whose heat is fed to the abutment region S at a low temperature

  sheet 2 and film 3, first has its temperature

  which is detected by the temperature detector 9 and then receives the controlled radiant heat, which comes from the irradiation lamp 7B whose operation is controlled by the phase control circuit 10 according to the signal of the temperature detector 9, so as to It is possible to again reach the abutment region S to heat the sheet 2 and so on. As a result, the temperature

  from the roll 1B to the abutting region S can be stable

  at the desired level at any time.

  As a similar state is applied to the other roll 1A, it is sufficient to provide the temperature detector 9 only on a roll if the two rollers

1A and 1B are similar.

  On the other hand, the lamps 7A and 7B are not formed so that their radiant heat emission states change instantaneously in response to the signal from the temperature detector 9, but in reality they are controlled with a predetermined delay. As a result, either by choosing the positioning positions of the temperature detector 9 according to the rotational speed of the rollers 1A and 1B or by adjusting the delay of the response, the radiating heats of the lamps 7A and 7B, which are controlled according to the temperature at the outer circumference portion which is described, can be emitted when the outer circumferential portion whose temperature is detected by the temperature detector 9 reaches the

  irradiated region HB, so the temperature on the circumferences

  The outer regions of the rollers 1A and 1B to reach the abutting region S can be maintained more reliably at the desired constant level. Moreover, in the case where the temperature detector 9 is arranged in a position such that it receives directly the emission of the heat-radiating lamps 7A and 7B, it is sufficient to provide a shielding plate so as to prevent the

  temperature detector 9 which is described to be direct-

  irradiated by radiant heat. If the temperature detector 9 is arranged in a position such that it is protected by the roller 1A as in the illustrated example, the construction is simplified because the

  shielding plate can be removed in this case.

  Fig. 6 is an explanation view showing an example of the construction of the aforementioned temperature detector 9. In this example, a plate 21 for holding an element, which is made of a plate made of an elastic metal such as a phosphor bronze or stainless steel, is forced to have a fixed end-end on the reflecting plate 6e. above mentioned, its other end being warped to form a heat receiving portion 22 which is slightly in elastic contact with the outer circumference of the roll 1B, and a temperature sensing element 23, preferably formed of a thermistor, is fixed on this surface of the heat-receiving portion 22 opposite to the other surface contacting the roller 13. According to the construction just described, the temperature on the outer circumference of the roller 1B can be reliably detected. without damaging the element detecting the

temperature23 and the roller 1B.

  Although the foregoing description is directed

  in the case where the sheet 2 has its two covered surfaces, according to the present invention, a device for covering only one surface of the sheet 2 can be formed by arranging a heat irradiation lamp in a position to make facing one of the rollers 1A or 1B, with a temperature detector arranged with respect to

the other roller considered.

  As will be understood from the reading of the

  According to the present invention, since the external circumferences of the rollers, from which heat is transferred to the sheet surfaces, are heated by the radiant energy from the lamps, it is possible to provide a device covering the surface of the lamps. a sheet for raising the temperature of the external diameters of the rollers in a short time, thus with a short preparation time. Moreover, since the current to be supplied to the heat irradiation lamps is controlled by the phase control circuit after these lamps have been switched on, it is also possible to provide a device for covering the surface of a sheet. validated to stabilize the heating temperature and to make the temperature at the abutting region of the

  rolls, reliably, to the desired constant level.

  1.- Device for covering the surface of a sheet, characterized in that it comprises: two rollers (1A, 1B) forming a slipper roll (4) for transferring a sheet (2) at least one of which The surface is covered with a plastic film and a heat irradiation lamp (7A or 7B) arranged to face the outer circumference of at least one of said rollers during sound. butting on said plastic film; and a phase control circuit (10) for controlling the electric current that is to be applied to said lamp; said phase control circuit comprising a triac (TRC) connected in series with said slape, a temperature detector (9) for detecting the temperature on the outer circumference of the roll which is heated by said lamp, and a control circuit (CC ) to control the conduction duration of said triac according to the

  signal from said temperature detector.

  2.- Device according to claim 1, characterized in that the aforesaid temperature sensor is formed of a positive type thermistor (PTC) and in that the aforementioned control circuit comprises a capacitor (C1) controlling the conduction time of

  triac which is connected in series with said thermistor.

  3.- Device according to claim 1, characterized in that the aforesaid temperature sensor is formed of a negative type thermistor (NTC), and in that the aforementioned control circuit comprises a capacitor (C1) controlling the time of conduction of the triac and which is connected in parallel with said thermistor. 4.- Device according to any one of

  preceding claims, characterized in that the

  The aforesaid temperature sensor operates to detect the temperature on the outer circumference of the aforementioned roller, which faces the aforementioned irradiation lamp, upstream of the irradiated region of the outer circumference.

of said roll.

  5.- Device according to claim 4, characterized in that the aforesaid temperature sensor is placed downstream of the abutment region (S) of the aforesaid roller o said roller abuts on the other roller and in the vicinity of said butting region in order to be released from the direct emission of radiant heat

from the aforementioned lamp.

  6.- Device according to claim 5, characterized in that the aforesaid temperature sensor comprises a holding plate (21) made of a plate of an elastic metal and having a portion (22) receiving

  the heat that is in elastic contact with the circumference

  the above-mentioned roller, whose temperature

  must be detected, and a temperature sensing element

  ture (23) attached to the surface of the holding plate

  faces the part receiving the heat.