FIELD OF THE INVENTION

[0001] The present invention relates to safety and braking arrangements for laminating machines, and more specifically the invention pertains to a fiber optic safety and dynamic braking arrangement for a laminating machine.

BACKGROUND OF THE INVENTION

[0002] Laminating processes generally include a pair of rotatably mounted cylinders or rollers, or a rotatably mounted roller(s) and a flat surface that form a nip through which materials are fed for lamination. Inasmuch as the rollers and flat surface are relatively firmly mounted, it is desirable to protect the nip between the same from the entry of foreign objects that may damage the lamination. More importantly, governmental safety organizations and manufacturers alike seek to elevate user safety in operation of laminating machines. The placement of user appendages between the rollers and flat surface may well result in considerable injury.

[0003] Safety shields and the like have long been used to enhance user safety during operation of laminating machines. Inasmuch as such safety shields are sometimes perceived by operators to obstruct their vision of or access to the machine, however, operators sometimes seek to operate the machine without the benefit of such safety shields. While the shields are frequently tied to the operation of the machine, such that the machine will not operate unless the shield is in the appropriate position, operators sometimes "jury-rig" the machine to operate, even when the shield is not properly disposed, contrary to the intent and best efforts of the manufacturers. While manufacturers have made various attempts to enhance safety and to minimize the possibility of tampering with safety features, each has its limitations or has met with limited success.

OBJECTS AND BRDZF SUMMARY OF THE INVENTION

[0004] The invention provides a plurality of fiber optic sensors disposed to monitor the nip between a pair of rollers or between roller(s) and a surface, such as a tray table,

as well as a dynamic braking system that provides stops the roller(s) as quickly as possible. Preferably, at least two fiber optic sensors are provided at the nip between a roller and a tray table and, preferably, at least three fiber optic sensors are provided at the nip between a pair of rollers in order to cover the entire vicinity close to the nip. The individual sensors are located and oriented relative to one another and the nip such that they provide a light mask profile that effectively covers and monitors the entire area close to the running nip.

[0005] Inasmuch as the sensors are disposed in such close proximity to the nip, it is essential that the machine stop as quickly as possible, preferably within a time period considered acceptable by safety agencies. Rapid braking is particularly important in some wide format laminating machines, for example, which typically run at speeds on the order of 25 feet per minute. In other words, as dynamic braking arrangement must stop the machine faster than an average human hand can move into the running roller nip.

[0006] The dynamic braking device of the invention preferably includes a resistor with a relay that is connected across the voltage applied to the motor. When the optic system is obstructed by a finger or the like, power is cut to the motor. When power is cut to the motor, the remaining residual voltage in the motor coil is also short circuited, emptying any residual voltage from the motor coil to stop the motor dead. The speeds from which a motor may be instantly stopped as a result of the dynamic braking device can vary from 1 to 20 feet per minute.

[0007] In summary, the resulting light mask profile and dynamic braking arrangement provides an essentially fail-safe system that meets applicable safety standards. The arrangement prevents a safety standard 12 mm test finger from going into the running nip and that meets known safety standards for lamination machinery.

[0008] These and other objects and advantages of the invention will be apparent to those skilled in the art upon reading the following summary and detailed description and upon reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIGURE 1 is a schematic side elevational view of rollers of a laminating machine with a fiber optic sensor arrangement constructed in accordance with teachings of the invention.

[0010] FIG. 2 is an enlarged, fragmentary view of the nip formed between the rollers of FIG. 1.

[0011] FIG. 3 is a schematic side elevational view of a roller and tray table arrangement of a laminating machine with a fiber optic sensor arrangement constructed in accordance with teachings of the invention.

[0012] FIG. 4 is an enlarged, fragmentary view of the nip formed between one of the rollers and the tray table of FIG. 3.

[0013] FIG. 5 is a schematic of a dynamic braking arrangement constructed in accordance with teachings of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Turning now to the drawings, there is shown in FIG. 1, an exemplary laminating machine 20. The laminating machine 20 illustrated is by way of example only and is not intended to be used to limit the application of the invention in any way. The laminating machine 20 includes a pair of rollers 22, 24 that meet to form a nip 26 therebetween. One or both of the rollers 22, 24 are driven by a motor, and may be heated by any appropriate arrangement. In use, a film or other first sheet (not shown) is typically laid or delivered along one of the rollers 22, while a second sheet (not shown) to be laminated is laid or delivered along a second of the rollers 24. As the upper roller 22 rotates in a counterclockwise direction and the lower roller 24 rotates in a clockwise direction, the first and second sheets progress into and through the nip 26 to be laminated together. For the purposes of this disclosure, the space disposed substantially parallel to the path of the respective sheets as they approach the nip 26, here, substantially concentric to the outer surfaces of the first and second rollers 22, 24, will

be described generally as the first and second sheet zones 32, 34, respectively. The space located prior to the entry into the nip 26 through which a zone of safety is desired will be described generally as the entry safety zone 36. The entry safety zone 36 is typically small enough to permit efficient usage of the machine, yet large enough to inhibit the entry of foreign objects into the space prior to the nip 26. According to known safety standards for lamination machines, a 12 mm "test finger" must not be able to enter the running nip.

[0015] According to an aspect of the invention, a plurality of fiber optic sensors 40, 42, 44 are disposed and arranged such that they are directed along the entry safety zone 36 to the nip 26. It will be appreciated by those of skill in the art that the fiber optic sensors 40, 42, 44 may be of any appropriate design, but typically include a sender, which transmits a beam of light, and a receiver, which receives the transmitted beam. The sender is preferably generally disposed at one end of the rollers 22, 24, while the receiver is generally disposed at the opposite end of the rollers 22, 24 such that the beam is transmitted through the entry safety zone 36. When a finger 46 or other foreign object enters the entry safety zone 36, the finger 46 interrupts the beam from the transmitter to the receiver of a given fiber optic sensor 40, 42, 44. This tripping of the fiber optic sensor 40, 42, 44 causes power to the motor driving roller(s) 22, 24 to be cut. In this way, if the operator's extremities or clothing enters the entry safety zone 36 disposed prior to the moving nip 26, the power to the motor is cut, causing the driving rollers 22, 24 to stop to prevent or at least minimize the possibility of the extremity or clothing being drawn into the nip 26.

[0016] While any number of the sensors 40, 42, 44 may be provided so long as the safety zone 36 of is effectively protected, three such sensors 40, 42, 44 are preferably provided. In the currently preferred embodiment, the sensors 40, 42, 44 are 12 mm in diameter and are PICO fiber optic sensors. Similarly, while the sensors 40, 42, 44 may be disposed and masked in any appropriate orientation so long as the safety zone 36 is effectively protected. In the embodiment of FIGS. 1 and 2, the sensors 40, 42, 44 are disposed in a substantially vertical, linear alignment with 1 mm between adjacent sensors 40 and 42, 42 and 44, and with the top and bottom sensors 40, 42 disposed 6

mm from the surface of the rollers. Masking of the sensors 40, 42, 44 to present a slots 50, 52, 54 on both the sender and receiver having a width of 2 mm, with the slots disposed at a positive 45° angle, a 90° angle, and a negative 45° angle, respectively, as illustrated in FIGS. 1 and 2 has been found to be effective. It will be appreciated by those of skill in the art, however, that alternate placement, masking, and disposition may likewise provide adequate protection of the safety zone. By way of example only, masking with slots on the order of 1.5-5 millimeters may likewise be effective.

[0017] A similar laminating machine 60 arrangement is shown in FIGS. 3 and 4. The laminating machine 60 likewise includes a pair of rollers 62, 64 that meet to form a nip 66 therebetween. This embodiment of the laminating machine 60, however, further includes a tray table 70 disposed prior to the nip 66 that may be used to support a second sheet as it approaches the nip 66 to be laminated with a first sheet approaching the nip 66 from the first roller 62. Thus, a preliminary nip 76 is formed between the first roller 62 and the table 70 such that it is desirable to prevent foreign objects from entering the preliminary nip 76. In this embodiment, the space located prior to the entry into the preliminary nip 76 through which a zone of safety is desired will be described generally as the entry safety zone 86. The space disposed substantially parallel to the path of the respective sheets as they approach the preliminary nip 76, here, substantially concentric to the outer surface of the first roller 62 and parallel to the tray table 70 will be described generally as the first and second sheet zones 82, 84, respectively. As with the entry safety zone 36, the entry safety zone 86 is typically small enough to permit efficient usage of the machine, yet large enough to inhibit the entry of foreign objects into the space prior to the preliminary nip 76.

[0018] In the embodiment shown in FIGS. 3 and 4, only two fiber optic sensors 90, 92 are required, although additional sensors may be provided. As with the previous embodiment, the sensors 90, 92 are 12 mm, disposed 1 mm apart and in substantially vertical, linear alignment 6 mm both from the first roller 62 and from the tray table 70. It has been determined that sensors 90, 92, so disposed with the sender and receiver masked with a 2 mm slot 100, 102, disposed at positive 45°, respectively, as illustrated, provide an effective entry safety zone 86. It is envisioned, however, that alternate

masking arrangements will likewise be suitable for the embodiments of both FIGS. 1-2 and 3-4, such as making providing a round opening having, for example, an opening on the order of 1-6 mm.

[0019] As with the first embodiment, however, those of skill in the art will appreciate an alternate number of sensors may be provided, disposed and/or masked, so long as the desired zone of safety is effectively protected.

[0020] According to another aspect of the invention, in order to provide increased protection that foreign objects entering the entry safety zone 36, 86 will not enter the nip 26, 76, the lamination machine 20, 60 is preferably provided with a dynamic braking device, that is, the machine 20, 60 is preferably provided with an arrangement that reliably arrests rotation of the rollers 22, 24, 62, 64 as rapidly as possible. In the preferred embodiment (see FIG. 5), the dynamic braking device includes a resistor R that includes a relay CR ₁ connected across the voltage applied to the motor M. When the power is cut due to obstruction of the beam of one or more of the optic sensors 40, 42, 44, 90, 92, the remaining voltage in the motor coil is short-circuited. As a result, the motor coil is emptied of any residual voltage, which stops the motor dead. It has been determined that the motor of a machine running at speeds from 1 to 20 feet per minute may be effectively stopped by this arrangement.

[0021] In order to maximize user safety during both forward and reverse modes of operation, in a preferred arrangement of the invention, fiber optic sensors are disposed at both the main roller forward nip entrance and the pull roller reverse nip entrance. During forward operational mode, the fiber optic sensors at the pull roller reverse nip are deactivated; alternately, in the reverse mode of operation, the fiber optic sensors at the main roller forward nip are deactivated. It is noted that when fiber optic sensors are utilized at the pull roller reverse nip for use in the reverse mode of operation, a pair of pressure plates are preferably provided at the back table to prevent the fiber optic sensors from stopping the machine when curled output is detected. Preferably, the plate depth should be on the order of six or more inches deep and disposed with the top of the plate not more than 12 mm from the upper surface of the back table, the plate being

spaced from the back table surface a sufficient distance to provide clearance for machine output. A second plate may likewise or alternately be provided as an "in-feed" plate to prevent media from curling upwards upon the entrance into the running forward roller nip.

[0022] In use, if the fiber optic beams are being obstructed while the upper roller, be it the main roller or an upper pull roller, is moving downward to close the nip, the upper roller moves up immediately rather than continuing its movement to close the nip. During operation in either the forward or reverse mode, when the fiber optic beam is interrupted or any safety circuitry is opened, the machine stops instantly.

[0023] Those of skill in the art will appreciate that a laminating machine may typically be operated by way of a control panel or a foot switch. In a currently preferred arrangement of a laminating machine in accordance with aspects of the invention, the control panel cannot be utilized to override the circuitry to start the machine once a fiber optic beam has been interrupted or any safety circuitry has been opened. Rather, the operator can use only the foot pedal to override. As a result, the operator may only override the machine at a low voltage, as opposed to the high voltage utilized at normal operation. In the override mode, the operator may run the machine at only a low speed on the order of 3 feet/minute. Until the fiber optic beam is cleared and all safety circuits are closed, the machine will not run under normal operating conditions.

[0024] In order to return the machine to a normal, high voltage mode of operation once the beam is cleared and all safety circuits are closed, the operator preferably has a number of choices. First, from a stationary position, the operator may push the RUN button (of the control panel or the foot pedal to run the machine at the preset control panel knob speed. Second, if the operator has been utilizing the foot pedal to achieve a low voltage, low speed operation, the operator may merely release the foot pedal to stop the machine, and then press the foot pedal again to likewise start the machine as the original, preset control panel knob speed. Third, if the operator has been running the machine at the low voltage speed and wishes to seamlessly increase the speed of the machine to the normal, high voltage speed and running operation, the operator may then

go through a series of steps. More specifically, maintaining his foot on the foot pedal to maintain the low voltage speed, the operator may press and hold the RUN button switch on the control panel. The operator then releases the foot pedal, and the machine maintains the previous low forward speed, but at a high voltage. The operator may then use the "speed knob" to adjust the speed of the machine to the desired running speed.

[0025] In summary, the invention provides a safety arrangement for a laminating machine. The safety arrangement includes a plurality of fiber optic sensors arranged to cover an entry safety zone disposed prior to the nip such that a standard test finger of 12 mm entering the entry safety zone will obstruct at least one of the lights from the fiber optic sensor to cut power to the motor driving the rollers. When power is so cut, a dynamic braking arrangement provides for rapid arrest of the motor by short-circuiting the motor coil via a relay connected across the voltage applied to the motor.

[0026] While this invention has been described with an emphasis upon preferred embodiments, variations of the preferred embodiments can be used, and it is intended that the invention can be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the following claims. For example, while the plurality of sensors has been described as being disposed in a substantially vertical, linear arrangement, it will be appreciated that the sensors need not be disposed in exact vertical or exact linear alignment, but, rather, may be alternately arranged as in an arc, or an arrangement that covers an extended area.

[0027] All of the references cited herein, including patents, patent applications, and publications, are hereby incorporated in their entireties by reference.