Patent Publication Number: US-6660992-B2

Title: Label-sensing device for a labeling machine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a label-sensing device for a labeling machine, more particularly to a label-sensing device that can be adjusted to suit the actual ambient light condition. 
     2. Description of the Related Art 
     Commodities, such as beverage bottles, drug bottles, containers, and packaging boxes, are generally provided with a label to classify products, to indicate usage and other information, to display the trademark or logo of the manufacturer, etc. With the recent advancement in automation, automated attachment of labels to such commodities has taken the place of manual label attachment, and has become quite popular in the industry. 
     Referring to FIG. 1, a conventional label-sensing device for detecting movement of a label reel during a label-feeding operation of a labeling machine is shown to comprise a controller  1 , a digital-to-analog (D/A) converter  2  coupled to the controller  1 , a buffer  3  coupled to the D/A converter  2 , an infrared sensor  4  coupled to the buffer  3 , and a comparator circuit  5  coupled to the infrared sensor  4  and the controller  1 . The controller  1  provides a binary-encoded signal to the D/A converter  2 . According to the binary-encoded signal from the controller  1 , the D/A converter  2  generates a corresponding analog voltage that is provided to the buffer  3 . The infrared sensor  4  receives the analog voltage from the buffer  3 , and generates a sensing light output having an intensity that corresponds to the analog voltage. The comparator circuit  5  receives a detected output from the infrared sensor  4 , and compares the detected output with a predetermined reference voltage. The result of the comparison is provided to the controller  1  by the comparator circuit  5 . 
     FIG. 2 is a schematic electrical circuit diagram of the conventional label-sensing device of FIG.  1 . As shown, the D/A converter  2  has eight input pins (XD 0 -XD 7 ) coupled to the controller  1 . Thus, the controller  1  can provide 256 combinations of the binary-encoded signal to the D/A converter  2 , thereby enabling the latter to generate 256 different analog voltages. A transmitter side of the infrared sensor  4  receives the analog voltage from the D/A converter  2  via the buffer  3 . Thus, the intensity of the sensing light output at the transmitter side of the infrared sensor  4  depends on the magnitude of the analog voltage from the D/A converter  2 . The sensing light output is directed to pass through one end of a label reel (not shown), which is being fed by a labeling machine (not shown), before being received by a receiver side of the infrared sensor  4 . The label reel includes a backing paper strip and a plurality of labels releasably and successively adhered on the backing paper strip. The detected output at the receiver side of the infrared sensor  4  is weaker at portions of the label reel where the labels overlap with the backing paper strip, and is stronger at portions of the label reel where the labels do not overlap with the backing paper strip, e.g. at a clearance between each adjacent pair of the labels on the backing paper strip. The comparator circuit  5  compares the detected output from the receiver side of the infrared sensor  4  with a predetermined reference voltage that is set by resistors R 22 , R 23  of a voltage-divider circuit, and generates a high or low logic output when the detected output is lower or higher than the reference voltage. The logic output of the comparator circuit  5  is received by the controller  1  and is recorded by the latter. 
     It is noted that the accuracy of the label-sensing device is affected by the actual ambient light condition. It is thus desirable to provide a label-sensing device that can be adjusted to ensure proper operation regardless of the actual ambient light condition. 
     SUMMARY OF THE INVENTION 
     Therefore, the main object of the present invention is to provide a label-sensing device for a labeling machine that can be adjusted to suit the actual ambient light condition. 
     According to this invention, a label-sensing device is adapted for use in a labeling machine to detect movement of a label reel during a label-feeding operation of the machine. The label reel includes a backing paper strip and a plurality of label reels releasably and successively adhered on the backing paper strip. The label-sensing device comprises a power supplying circuit, an infrared sensor, a voltage amplifier, and a controller. The power supplying circuit is adapted to supply a predetermined regulated DC voltage output. The infrared sensor includes an infrared transmitter coupled to the power supplying circuit, and an infrared receiver that forms a clearance with the infrared transmitter. The clearance is adapted to permit passage of one end of the label reel therethrough. The transmitter generates a sensing light output with an intensity that corresponds to the regulated DC voltage output. The sensing light output is directed by the transmitter so as to be adapted to pass through said one end of the label reel before being received by the receiver. The receiver has a detected output with a weaker first intensity upon detection of a first portion of the label reel where one of the labels overlaps with the backing paper strip, and with a stronger second intensity upon detection of a second portion of the label reel where the labels do not overlap with the backing paper strip. The voltage amplifier is coupled to the receiver for amplifying the detected output. The voltage amplifier generates a first signal when the detected output has the first intensity, and a second signal when the detected output has the second intensity. The controller, which is coupled to the voltage amplifier, converts the signal from the voltage amplifier into a corresponding detected value, and compares the detected value with an initial reference value to determine whether the first portion or the second portion of the label reel has passed through the clearance of the infrared sensor. 
     In the preferred embodiment, the controller automatically adjusts the initial reference value to be higher than the detected value corresponding to the first signal from the voltage amplifier upon detection by the controller that the initial reference value is lower than the detected value for the first signal, and to be lower than the detected value corresponding to the second signal from the voltage amplifier upon detection by the controller that the initial reference value is higher than the detected value for the second signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which: 
     FIG. 1 is a block diagram showing a conventional label-sensing device; 
     FIG. 2 is a schematic electrical circuit diagram of the conventional label-sensing device of FIG. 1; 
     FIG. 3 is a block diagram of the preferred embodiment of a label-sensing device according to the present invention; 
     FIG. 4 is a schematic electrical circuit diagram of the preferred embodiment; and 
     FIG. 5 is a perspective view showing a labeling machine that incorporates the preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 3 and 4, the preferred embodiment of a label-sensing device according to the present invention is shown to comprise a power supplying circuit  10 , an infrared sensor  20  coupled to the power supplying circuit  10 , a voltage amplifier  30  coupled to the infrared sensor  20 , and a controller  40  coupled to the voltage amplifier  30 . 
     The power supplying circuit  10  includes a voltage regulator  11 , and supplies a predetermined regulated DC voltage output. 
     The infrared sensor  20  includes an infrared diode transmitter  21  connected in series to a resistor  23 . The series combination of the transmitter  21  and the resistor  23  are connected in parallel to the power supplying circuit  10  and to a capacitor C 1 . The transmitter  21  generates a sensing light output with an intensity that corresponds to the regulated DC voltage output. The infrared sensor  20  further includes an infrared diode receiver  22  connected in series to a resistor  24 . A detected output from the infrared sensor  20  is obtained from the junction of the receiver  22  and the resistor  24 . 
     In practice, as shown in FIG. 5, the sensing light output from the transmitter  21  is directed to pass through one end of a label reel  500 , that is being fed by a labeling machine  600  through a clearance  211  that is formed between the transmitter  21  and the receiver  22 , before being received by the receiver  22 . The label reel  500  includes a backing paper strip  50  and a plurality of labels  51  releasably and successively adhered on the backing paper strip  50 . The detected output at the receiver  22  has a weaker first intensity upon detection of first portions of the label reel  500  where the labels  51  overlap with the backing paper strip  50 , and a stronger second intensity upon detection of second portions of the label reel  500  where the labels  51  do not overlap with the backing paper strip  50 , e.g. at a clearance between each adjacent pair of the labels  51  on the backing paper strip  51 . Of course, the magnitudes of the first and second intensities are affected by the physical characteristics, e.g. paper quality, thickness and transparency, of the backing paper strip  50  and the labels  51 . 
     The voltage amplifier  30  is connected to the junction of the receiver  22  and the resistor  24 , and amplifies the detected output from the infrared sensor  20  in a conventional manner. Thus, the voltage amplifier  30  generates a first signal when the detected output has the first intensity, and a second signal when the detected output has the second intensity. 
     The controller  40  receives the first and second signals from the voltage amplifier  30 . When operated in an initialization mode, the controller  40  converts the first signal into a 12-bit first detected value, and further converts the second signal into a 12-bit second detected value. The controller  40  then determines an initial reference value between the first and second detected values. Thus, when the controller  40  is operated in a normal mode, the controller  40  is able to determine whether the detected portion of the label reel  500  is one where the labels  51  overlap with the backing paper strip  50  when the detected value for the signal from the amplifier  30  is lower than the initial reference value, or one where the labels  51  do not overlap with the backing paper strip  50  when the detected value for the signal from the amplifier  30  is higher than the initial reference value. For example, assuming that the initial reference value is set at 300, if the detected value is 250, this indicates that the detected portion of the label reel  500  is one where the labels  51  overlap with the backing paper strip  50 , and if the detected value is 600, this indicates that the detected portion of the label reel  500  is one where the labels  51  do not overlap with the backing paper strip  50 . 
     The controller  40  samples the signal from the amplifier  30  at a rate of about 25000 times per second. In the event of a change in the ambient light condition, the initial reference value might have to be adjusted so that the initial reference value is between the detected values for the different portions of the label reel  500  in order to achieve accurate detection of the movement of the label reel  500 . In other words, upon detection by the controller  40  that the initial reference value is lower than the first detected value, the initial reference value is adjusted to a new value higher than the first detected value. Accordingly, upon detection by the controller  40  that the initial reference value is higher than the second detected value, the initial reference value is adjusted to a new value lower than the second detected value. 
     With the inclusion of the label-sensing device of this invention in a labeling machine, the leading edges of the labels  51  on the label reel  500  can be accurately positioned with respect to a label applicator plate  60  when attaching the labels  51  to containers (not shown). 
     Unlike the conventional label-sensing device described beforehand, the intensity of the sensing light output from the infrared transmitter  21  is constant since the latter is driven by a regulated DC voltage output from the power supplying circuit  10 . In addition, the controller  40 , which continuously samples the signal from the amplifier  30 , is capable of adjusting a reference value therein to ensure that the latter is between the detected values for different portions of the label reel  500  in order to compensate for changes in the ambient light condition and to achieve accurate detection of the movement of the label reel  500 . 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.