Patent Publication Number: US-4547249-A

Title: Sensor for label transporting equipment

Description:
CROSS REFERENCE TO RELATED APPLICATIONS AND PUBLICATIONS: 
     The subject matter of this application is related to that of our copending application entitled &#34;Labeling Apparatus With Improved Label Transport Control&#34;, Ser. No. 593,042 filed Mar. 23, 1984. 
     FIELD OF THE INVENTION 
     The present invention relates to automatic or semiautomatic devices applying labels to objects such as crates or boxes. In particular, the transport for the band carrying the labels is a step by step transport which must be stopped when the labels are in a particular position relative to a device removing the labels from the band. The present invention is concerned with a device generating a signal stopping the transport when each label is properly positioned. 
     BACKGROUND OF THE INVENTION 
     In conventional labeling equipment of the above-described type, a series of labels is carried by the band, with gaps between consecutive labels. Further, control holes are in the band and these control holes are sensed either by an air cell or by a light cell. The fact that such control holes must be provided is in itself a disadvantage. Additionally, the holes may not be properly formed, causing the band transport to malfunction. In addition, the velocity with which the band may be advanced must be kept within predetermined limits, since the time that the holes are within the range of the feeler or sensor must exceed the response time of the scanning apparatus including the cell. This problem exists mainly when air cells are used, since these have a relatively high response time. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to furnish an improved scanning device which allows high band velocities and, preferably, obviates the need for control holes while still allowing a reliable control of the transport. 
     According to the present invention, the scanning device consists of a backing or support positioned on the side of the band which does not carry the labels. A feeler is provided which is pressed against the side of the band carrying the labels, so that the feeler position changes either at the edge of a label or when the gap between labels is being sensed. The change in position of the feeler causes a corresponding change in the position of bar linked to the feeler mechanism which, in turn, switches either an air or a light cell from a first to a second state. When the cell is in the second state, the signal stopping the transport is generated. Additionally, a delay member, such as a spring, may be provided to cause the bar to maintain the switch in the second state for a longer time than the time corresponding to the sensing of the gap between labels, so that higher band transport velocities may be used. 
     According to a preferred embodiment, the feeler is connected to an angle lever which pivots about an axis parallel to the band and perpendicular to its direction of advance. The feeler is connected to one arm of the lever which, in turn, is pushed against the band by means of a spring. The second arm of the lever extends perpendicularly to the first arm and supports one end of a bar whose other end switches the state of the air or light cell. One side of the lever is provided with a stop which carries along the bar when the lever pivots in response to sensing of the gap by feeler. The bar is moved against the force of a weak spring affixed to the lever and continues its motion after the lever has stopped and even after the lever has reversed direction. This increases the time that the cell is in the state generating the signal for stopping the transport. The force of the spring finally causes the bar to be returned to the position abutting the stop. 
     The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in conjunction with the accompanying drawing. 
    
    
     FIG. 1 is a top view of labeling apparatus with a mechanical scanning device; and 
     FIGS. 2a and b show the scanning device in the rest and activated position, respectively. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT: 
     The labeling equipment illustrated in FIG. 1 may be used, for example, for automatically applying self-adhesive labels to block-and-tackle boxes transported past the device on one side of a guide rod 12. 
     A band 16 is pulled from the supply reel 14 and carries self-adhesive labels at predetermined distances from one another on the side facing downward in FIG. 1. The band is transported past a scanning device 20 and a guide roller 22 to a label removing station. This consists of a sharp edge 24 at which the direction of advance of the band is changed so that the first label 18 is removed from the band and pushed forwards under a roller 26 onto a flap 28, while the empty band 16&#39; is directed towards a take-up reel 32 by means of a second guide roller 30. The take-up reel is driven in a stepwise manner in the direction of arrow 34. 
     Application of the label to the box and the subsequent step of band transport is initiated by the output signal of an optical scanner 36. Scanner 36 recognizes markings on the box and furnishes information according thereto to a central pneumatic control 38. During labeling, flap 28 with self-adhesive label 18 is pushed against the side of the passing box by means of a pneumatic cylinder 29. The box then passes a brush 40 which causes the label, which is already sticking at its front edge, to be firmly affixed to the wall of the box throughout its length. During, or immediately after this labeling process, the next transport step is initiated by central control 38, causing the next self-adhesive label 18 to arrive at edge 24. Thereafter, the signal from scanner 20 causes the band transport to be stopped again, after the band has been transported by a length equal to that of one label. 
     As can be seen from FIGS. 2a and b, scanning device 20 consists of an angle lever 46 rotatable about an axis 44. A feeler roller 48 is eccentrically mounted on the angle lever, the two being pressed against the label-carrying surface 52 of the conveyer band by a strong leaf spring 50. A supporting plate 56 for the band is provided on the side opposite the roller. In addition, a long flat bar 58 is connected to angle lever 46 for rotation about an axis 60 parallel to axis 44. End 62 of bar 58 extends over perpendicularly extending arm 64 of the angle lever, while its free end 66 rests on a flat table 68 and controls the passage of air through an air barrier 70. The contacting surface in the region of arm 64 is bounded on the one side by a stop 72 and on the opposite side by a flat spring 74 fastened near axis 60. 
     As long as band 16 is stationary, feeler roller 48 is pressed against the surface 52 of a self-adhesive label 18 present in this position. The free end 66 of bar 58 blocks the air passage in air cell 70, i.e. prevents air from reaching a receiving nozzle 76. This condition is maintained while the band is transported in the direction of arrow 80, as long as roller 48 still presses against surface 52 of label 18. However, as soon as the trailing edge 78 of label 18 passes the scanning location, roller 48 is pushed by spring 50 with simultaneous rotation of level 46 into the depression formed by gap 42 between the labels. Immediately thereafter, the roller crosses leading edge 78&#39; of the next following label 18&#39; and is lifted to the surface 52 of the latter. During this pivoting, bar 58 is first carried along by stop 72, so that it already has moved some distance out of the air passage 46 of air cell 70, as illustrated in the solid lines in FIG. 2b. 
     To assure a proper response from air cell 60, the above condition must be maintained for a time period in the order of several milliseconds to ten milliseconds. If the connection between lever 46 and bar 58 were a rigid connection, this could only be accomplished by a relatively slow band transport and/or large gaps 42 between individual labels 18, 18&#39;. To avoid this problem, bar 58 is pivotably mounted on lever 46. Thus when roller 48 enters into the gap between labels, bar 58 is carried along by stop 72 and is accelerated to the angular velocity of lever 46. Because of its inertia, bar 58 continues to rotate in the original direction against the force exerted by weak spring 74, even after the rotation of lever 46 has been stopped as roller 48 enters gap 42 and subsequently reversed when the roller is lifted by subsequent label 18&#39;. Thus the time that air cell 70 is open can be a multiple of the time that roller 48 rests in the gap between two labels. The exact multiple is determined by choice of the spring constant of spring 74. Thus reliable operation of air cell 70 can be achieved even at high band transport speeds and for small gaps 42. At high band transport velocities, however, the delayed response of air cell 70 causes the band transport to be stopped only when the label 18&#39; which follows the sensed gap 42 has already passed partially by roller 48. This creates no problem as long as the exact distance is known. 
     While the invention has been illustrated in preferred embodiments, it is not to be limited to the structures shown, since many variations thereof will be evident to one skilled in the art and are intended to be encompassed in the present invention as set forth in the following claims.