Abstract:
The inventive label sensing device includes a label detector within a housing. The label detector includes a bearing assembly serving as a piston, the bearing assembly having a roller bearing for riding over label material. The roller bearing moves the bearing assembly vertically as the roller bearing rides over the label material based on the height differential of the label and the label substrate. The bearing assembly is in contact with the first end of a lever arm at a pivot point located on the bearing assembly. As the bearing assembly moves up and down, the first end of the lever arm moves responsive to movement of the pivot, generating an amplified signal in the second end of the lever arm, proportional to movement of the roller bearing. Provided at a location adjacent to the second end of the lever arm is a proximity sensor for detecting the movement of the second end of the lever arm within a soft switching region.

Description:
BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     This invention relates to an apparatus and method for detecting labels and more particularly to an apparatus and method for detecting labels removably adhered in a strip-like fashion on a substrate, combining mechanical and proximity sensing. The movement of a mechanical sensor detects the leading edge of the label while a lever arm amplifies that movement for detection by a proximity sensor, thereby providing a label detecting method and apparatus functioning accurately regardless of wear on the mechanical system. 
     B. Prior Art 
     It is known in the art of labeling and labeling machines to provide a label detector. A label detector is required and usually incorporated into a labeling device to sense the leading edge of a label on the label&#39;s backing material for synchronizing the labeling machine to properly register the label for application to the product. Four types of label detectors are generally known in the art of labeling: optical thru-beam, optical reflective, capacitive, and mechanical. 
     First, it is known to use a labeling machine employing an optical thru-beam for label detection. The optical thru-beam label detecting device employs a light beam from a source positioned above the label and a receiver positioned below the label backing paper stock. The optical thru-beam detector senses the label by analyzing the differences in light intensities between the backing material opacity and the label with backing material opacity. The main disadvantage of an optical thru-beam label detector is its inability to detect clear or translucent labels because the difference in light intensity between the backing material opacity and the label with backing material opacity is negligible and difficult to analyze. 
     Second, it is also known to use a labeling machine employing an optical reflective technique to detect labels. The optical reflective technique for detecting labels uses a light source and a receiver positioned above the label at an incident angle. This type of device detects the label by sensing the difference in reflective properties between the backing paper and the label. An optical reflective detector employing this technique, however, requires extremely precise positioning and often produces “false triggers” on different printed regions of the label being detected. 
     A third method for detecting labels known in the art is described in Herbst, Jr. U.S. Pat. No. 5,650,730 (hereinafter “&#39;730 Patent”). The &#39;730 Patent discloses a label detector using a capacitive technique. The capacitive label detector described in the &#39;730 Patent detects a label by calculating the difference in the dielectric measurement between the backing material without the label and the backing material with the label. It is apparent to those skilled in the art, however, that the capacitive label detector is deficient because it cannot detect labels containing conductive material, such as foil labels. Additionally, this type of label detector is not preferred because it cannot detect labels using conductive inks, particularly carbon based black ink, an ink very common on labels. 
     Finally, it is known to provide a mechanical label detector using a mechanical switch to sense the difference in thickness between the backing material without the label and the backing material with the label. The thickness differential can be as small as 0.004 inches and still be detected. Mechanical label detectors generally use a high precision mechanical switch mounted to a pin or bearing, which rides over the label material. The switch must be adjusted to open and close exactly where the small motion occurs. In other words, the mechanical label detector has a small finite switching margin. The drawback to the conventional mechanical label detector, however, is the mechanical label detector requires extremely precise adjustment due to the small finite switching margin reflected in the thickness differential. These kinds of adjustments often are difficult to perform. Another drawback to the conventional mechanical label detector is that the detector is frequently thrown out of adjustment from any wear in the system requiring frequent tinkering and replacement of parts. 
     SUMMARY OF THE INVENTION 
     The inventive mechanical label sensing apparatus comprises a label detector placed within a housing. The label detector comprises a bearing assembly serving as a piston, the bearing assembly having a roller bearing for riding over label and label backing material. The roller bearing moves the bearing assembly up and down as the roller bearing rides over the label material based on the height differential of the label and the label backing. The bearing assembly is in contact with the first end of a lever arm at a pivot point located on the bearing assembly. As the bearing assembly moves up and down, the first end of the lever arm moves over the pivot point generating an amplified physical movement of the roller bearing in the second end of the lever arm. Provided at a location adjacent to the second end of the lever arm is a proximity sensor for detecting the movement of the second end of the lever arm. The proximity sensor has a coil that generates a magnetic field. A switch in the proximity sensor is “tripped” when the second end of the lever arm enters the magentic field. 
     It is an object of the present invention to combine a proximity sensor with a mechanical label detector to provide a label detector with a “soft” switching field region. 
     It is another object of the present invention to provide a label detector that can withstand wear, yet maintain accuracy. 
     It is another object of the present invention to provide a label detector capable of detecting different kinds of labels including clear or translucent labels and labels containing conductive materials or conductive ink. 
     It is another object of the present invention to provide a label detector with a simple initial adjustment. 
     It is another object of the present invention to provide a label detector that produces a minimum of “false triggers”. 
     It is another object of the present invention to provide a label detector that is not affected by the dielectric or optical properties of the labels being detected. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevation view of the label detector. 
     FIG. 2 is a rear elevation view of the label detector. 
     FIG. 3 is a top plan view of the label detector. 
     FIG. 4 is a cross-sectional view of the label detector of FIG. 3 taken along the line  3 — 3 . 
     FIG. 5 is a schematic perspective drawing of the detection and signal amplification elements of the invention. 
     FIG. 6 is a front perspective view of the housing of the present invention. 
     FIG. 7 is a front perspective exploded view of the label detector and housing. 
     FIG. 8 is an enlarged front view of the label strip of the present invention illustrating the height differential Δh between the position of the roller bearing when in contact with the label substrate with a label and the space adjacent without a label. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1,  4  and  5 , the label detector  10  is disposed in a housing  12 , and comprises a bearing assembly  14  (FIG. 4) acting as a piston, a lever arm  16  pivotably resting upon bearing assembly  14  (FIG. 4) on a pivot point  18 , and a proximity sensor  20  located substantially adjacent one end of lever arm  16 . A biasing means  21  (FIG. 5) biases lever arm  16  against pivot point  18 . 
     As shown in FIG. 5, bearing assembly  14  of the preferred embodiment serves as a piston. Referring to FIG. 7 bearing assembly  14  is preferably cylindrical in shape having a closed flat top end  22  and an open bottom end  24  with a slot  26  dividing bearing assembly  14  into two sides  28 ,  30 . A shaft  32  extends through apertures  33  in bearing assembly  14  and through sides  28 , 30  of slot  26 . Shaft  32  is provided to mount a roller bearing  34  within bearing assembly  14 . Shaft  32  is preferably made of stainless steel although any appropriate material providing the strength and low friction qualities of steel may be employed. Roller bearing  34  has a bore  36  therethrough for rotatably mounting roller bearing  34  upon shaft  32 . 
     As shown in FIG. 4, shaft  32  is attached to bearing assembly  14  such that roller bearing  34  extends beyond the bottom end  24  of bearing assembly  14  allowing roller bearing  34  to come into contact with labeling substrate  37  (FIG. 8) and freely rotate over the substrate  37  (FIG. 8) without interference from bearing assembly  14 . Roller bearing  34  is preferably made of stainless steel although any appropriate material may be employed. In the disclosed embodiment, a roller bearing  34  with an outside diameter less than 5.0 mm is preferred. While a roller bearing  34  is preferred, other contact elements, such as a pin bushing or a ball bearing, may be operatively connected to bottom end  24  of bearing assembly  14 . 
     As shown in FIGS. 4 and 7, extending from approximately the middle of the top end  22  of bearing assembly  14  is a pivot point  18  in the form of a protuberance in the preferred embodiment. While it is preferred that pivot point  18  extend from the top end  22  of bearing assembly  14 , it is contemplated that pivot point  18  could alternatively extend from the bottom surface  38  of lever arm  16  and come in contact with the top end  22  of bearing assembly  14 . 
     Referring to FIG. 4, an optional lifting handle  39  may be provided to manually impart vertical movement to bearing assembly  14 . Referring to FIG. 7, if lifting handle  39  is included, a bore  40  is provided near the top end  22  of bearing assembly  14  for receiving the first end  42  of lifting handle  39  and affixing lifting handle  39  to bearing assembly  14 . It is understood that any appropriate means for affixing lifting handle  39  to bearing assembly  14  may be employed. Thus, the lifting handle  39  may be used to manually move bearing assembly  14  up and down allowing for easy insertion and processing of the labeling substrate  37 . Lifting handle  39  is preferably made of stainless steel, although any appropriate material may be employed. 
     As shown in FIG. 1, a pivotal lever arm  16 , having first and second ends  44 ,  46 , bottom surface  38  and top surface  48  pivots in a vertical plane about pivot point  18 . The bottom surface  38  of lever arm  16  near the first end  44  of lever arm  16  rests upon the pivot point  18 . The lever arm  16  is preferably made of stainless steel, although any appropriate material having the qualities of ferric steel may be employed. 
     As shown in FIG. 1, label detector  10  includes a proximity sensor  20  located substantially near the second end  46  of lever arm  16 . In the preferred embodiment, proximity sensor  20  is a proximity sensor located above the top surface  48  of second end  46  of lever arm  16 . Specifically, it is preferred that the proximity sensor  20  is an inductive proximity sensor. It is understood, however, by those skilled in the art that proximity sensor  20  may be located in any area near the second end  46  of lever arm  16  provided proximity sensor  20  is substantially close to the second end  46  of lever arm  16  to detect the vertical movement of the second end  46  of the lever arm  16 . In the preferred embodiment, proximity sensor  20  generates a magnetic field or a “soft” switching region of approximately 0.004 inches. Proximity sensor  20  detects lever arm  16  when the second end  46  of lever arm  16  either enters or exits the soft switching region. 
     As shown in FIG. 1, it is preferred to have the label detector  10  mounted in housing  12 . Referring to FIG. 6, the housing  12  is generally rectangular in shape, having an upper portion  52 , lower portion  54  and a mouth  56  providing entry to a slot  57  located between the upper and lower portions  52 ,  54 . As shown in FIG. 6, the upper portion  52  of housing  12  has a top surface  58 , front surface  60 , rear surface  61 , a first side surface  62  and a second side surface  63  (FIG.  2 ), a first end  64  and a second end  66 . 
     As shown on FIG. 6 located on the first side surface  62  of the upper portion  52  is a slotted portion or window  68  extending laterally only part of the way through housing  12 . Window  68  is a slotted portion on the first side surface  62  that extends from the first end  64  of upper portion  52  of housing  12  to the second end  66  of upper portion  52  of housing  12 . Referring to FIG. 1, inside the window  68  is an upper surface  69 , a lower surface  70 , a front surface  71 , a rear surface  72  and a back surface  73 . The back surface  73  of the window  68  is formed by the second side surface  63  (FIG. 2) of the upper portion  52  of the housing  12 . Window  68  is of sufficient dimensions to accommodate housing and operation of the lever arm  16  within the window  68 . 
     As shown in FIG. 6, on the top surface  58  of upper portion  52  of housing  12  is a first opening  74 . In the preferred embodiment, the first opening  74  is a cylindrical threaded bore, although any opening will suffice. First opening  74  of housing  12  is located near the second end  66  of upper portion  52  of housing  12 . First opening  74  extends from the top surface  58  of upper portion  52  of housing  12  through the upper surface  69  of window  68  into window  68 . As shown in FIG. 7, first opening  74  is sized to mount proximity sensor  20  such that proximity sensor  20  is able to detect movement of lever arm  16  within window  68  of housing  12 , as will be explained. 
     As shown in FIG. 6, a second opening  76  is located on lower surface  70  of window  68  near first end  64  of upper portion  52  of housing  12 . Second opening  76  extends from lower surface  70  of window  68  into slot  57  of housing  12 . Referring to FIG. 7, in the preferred embodiment, second opening  76  is a cylindrical bore sized to slidably accommodate bearing assembly  14  such that top end  22  of bearing assembly  14  reciprocates within window  68 . Bearing assembly  14  reciprocates within second opening  76  while roller bearing  34  operatively connected to bottom end  24  of bearing assembly  14  reciprocates within slot  57  of housing  12 . 
     As shown in FIG. 1, in the preferred embodiment, a pin  77  pivotably affixes first end  44  of lever arm  16  to back surface  73  of the window  68  near first end  64  (FIG. 6) of upper portion  52  of housing  12 . Bottom surface  38  of lever arm  16  near, but at a slight distance from, first end  64  of upper portion  52  of housing  12  rests upon pivot point  18 , causing lever arm  16  to pivot about pin  77  when upward or downward force is applied to lever arm  16  by bearing assembly  14  (FIG. 5) or by biasing means  21  (FIG.  5 ). Lever arm  16  is biased by biasing means  21  (FIG. 5) to maintain second end  46  of lever arm  16  in contact with lower surface  70  of window  68 . Referring to FIG. 5, it is preferred to have a spring  78  secured by a spring cap  79  as biasing means  21 . 
     Referring to FIG. 6, it is also preferred, although not necessary to the operation of the invention, to have a third opening  80  above and in alignment with second opening  76 . Third opening  80  extends from top surface  58  of upper portion  52  of housing  12  into window  68  of housing  12 . In the illustrated embodiment, third opening  80  is a cylindrical threaded bore that houses and maintains biasing means  21 . Spring cap  79  screws into third opening  80  and spring  78  extends into window  68  and presses against top surface  48  of lever arm  16 , biasing lever arm  16  against pivot point  18 . 
     As discussed previously, in the preferred embodiment, an optional lifting handle  39  may be provided. As shown in FIGS. 5 and 6, to accommodate lifting handle  39 , a fourth opening  82  may be provided in housing  12 . Fourth opening  82  is located on front surface  60  of upper portion  52  of housing  12  and extends into second opening  76  allowing lifting handle  39 , connected to bearing assembly  14 , to extend through fourth opening  82  and outwardly from housing  12 . Fourth opening  82  is of sufficient dimension to allow operation of lifting handle  39 . 
     As shown in FIG. 7, it is preferred, although not necessary, to provide a side plate  90  for covering window  68  and protecting the individual parts within window  68  of housing  12 . On first side surface  62  of upper portion  52  of housing  12  are four threaded apertures  92  for receiving screws  94 . Apertures  92  correspond to apertures  96  on housing  12  for receiving screws  94  for affixing side plate  90  to housing  12 . 
     Referring to FIG. 6, optional slotted grooves  97  are provided in the illustrated embodiment. Slotted grooves  97  modularize the label detector  10  and allow for easy insertion and removal of the label detector  10  within a labeling machine. 
     In operation, the leading edge of a labeling substrate material  37  (FIG.  8 ), to which a plurality of labels  98  are removably adhered in spaced relation, is passed through mouth  56  of housing  12  into slot  57 . The user lifts bearing assembly  14  with lifting handle  39  allowing the substrate  37  with labels  98  to pass underneath roller bearing  34 . Bearing assembly  14  is then lowered onto the labeling substrate  37 . The label substrate  37  with spaced labels  98  is continuously fed through slot  57  of housing  12 . As the label strip passes under roller bearing  34 , roller bearing  34  rotates over and in contact with the substrate  37  and labels  98 , causing bearing assembly  14  to move up as the circumferential surface of roller bearing  34  passes from a portion of label material containing only label substrate  37  to a portion of label material containing both a label  98  and the label substrate  37 . Similarly, biasing means  21  causes bearing assembly  14  to move down as roller bearing  34  passes back from a portion of label substrate  37  containing both the label  98  and the label substrate  37  to a portion of the label material containing only label substrate  37 . Thus, roller bearing  34 , and bearing assembly  14 , in turn, move upwards in an amount equal to the height differential Ah between the label substrate  37  with a label  98  and the label substrate  37  without a label  98 . 
     The up and down movement of bearing assembly  14  translates into an up and down movement of pivot point  18 , which in turn causes an amplified up and down movement in second end  46  of lever arm  16 . Thus, a small up and down movement of roller bearing  34  results in an amplified proportional movement of second end  46  of lever arm  16 . 
     Proximity sensor  20  generates a magnetic field or a “soft” switching field region. Proximity sensor  20  detects advancement of lever arm  16  towards or away from proximity sensor  20  when second end  46  of lever arm  16  either enters or exits the soft switching field region. 
     Thus, proximity sensor  20  is able to “detect” the leading and trailing edges of each label  98 . In operation with a labeling machine, proximity sensor  20  of label detector  10  then passes on a signal regarding the edges of the labels to the labeling machine, allowing the labeling machine to properly register the labels for application to a product. Because of the increased amplified movement of the lever arm  16  compared to the movement of the roller bearing  34  (approximately ten times greater than the switching resolution of the proximity sensor  20 ), when adjusting the location of the proximity sensor  20  there is 0.032 inches of margin rather than the 0.004 inches of margin required by most mechanical label detectors. 
     As a further result, the label detector  10  does not come out of sensing adjustment as the system wears due to the switching margin. Additionally, the label detector  10  is not affected by the dielectric or optical properties of the labels being detected. 
     The foregoing description of the embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The description was selected to best explain the principles of the invention and practical application of these principles to enable others skilled in the art to best utilize the invention in various embodiments and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention not be limited by the specification, but be defined by the claims set forth below.