Abstract:
Apparatus for detecting a defect during the formation of a container end having a stay-on-tab secured thereto, particularly when the defect is associated with a mis-located tab, in which a portion of the apparatus will be moved by the defect which movement is sensed and a signal is generated.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to the manufacture of container ends having a pull tab and more particularly to the detection of a defect occurring during the manufacture of container ends. 
     BACKGROUND OF THE INVENTION 
     Apparatus for the manufacture of container ends having pull tabs secured thereon for opening the container end is illustrated in a brochure published by The Stolle Precision Tool Company which is incorporated herein by reference thereto. As illustrated in the brochure, the container end manufacture involves two distinct operations. In one operation, a plurality of container end blanks are positioned in openings in a conveyor which is moved in a stepping operation so that the container end blank is moved between upper and lower dies at different positions to have a particular operation performed thereon. As illustrated in the brochure, a container end blank is intermittently moved to different positions to have a rivet stud formed therein. After that the score lines and indentation lines are formed therein. At the next position, the pull tab is placed over the rivet stud which is then smashed to hold the pull tab onto the container end blank. As illustrated in the brochure, the pull tabs are formed in a separate series of operations and, after being fully formed are positioned with an opening therein in alignment with the rivet stud. As illustrated in the brochure, the pull tabs are formed using a continuous strip of metal that is intermittently moved through a plurality of stations. As the pull tabs are being formed, they remain attached to the continuous strip of metal by one or more carry strips. The brochure illustrates two spaced apart carry strips between the tail of the pull tab and the continuous strip of metal. In another type of apparatus for the manufacture of the pull tab, only one carry strip is used and is located between the nose of the pull tab and the continuous strip of metal. The purpose of the carry strip or strips is to ensure that the pull tabs move with the continuous strip of metal. When the pull tab is separated from the continuous strip of metal to be placed over the rivet stud, a projecting portion of the carry strip remains attached to the nose of the pull tab or projecting portions of the carry strips remain attached to the tail of the pull tab. In either case, it is necessary to wipe down the pull tab to remove these projecting portions so that they will not result in deleterious contact with the user of the container on which the container end is secured either in the opening or using of the container. Therefore, the next position in the formation of a container end with a pull tab secured thereon is known as the tab wipe down assembly. In this position an upper die is provided with a portion to fold the projecting portion or portions so that the portion or portions have substantially the same configuration as the adjacent portions of the nose or tail of the pull tab. The upper die is also provided with a pilot that enters the finger hole of the pull tab to prevent lateral movement of the pull tab during the operation of the wiping operation so that no undue force is placed on the rivet to cause damage thereto. In the apparatus illustrated in the brochure, the conveyor carrying the container blanks has three rows of openings and moves at the rate of speed so that more than six hundred cans per minute in each row are passed through the various positions. Therefore, it is desirable to detect any defect in the production of the container ends as soon as possible to avoid the waste of a considerable amount of metal. There are many different types of causes which result in defects associated with the container ends. As illustrated on the front page of the brochure there are a variety of container ends having a pull tab secured thereon. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This invention provides apparatus for detecting a defect in the manufacture of container ends having a pull tab secured thereto wherein the defect prevents a portion of the detecting apparatus from reaching its lowermost position in relation to the lowermost position of an upper die in which it is located and is preferably located in the tab wipe down assembly of apparatus used in the production of a variety of container ends having a pull tab secured thereto as described above. 
     In a preferred embodiment of the invention, the detecting apparatus comprises a modification of the upper die used in the tab wipe down assembly. At this location, the lower die is stationary and the upper die moves in a longitudinal direction toward or away from the lower die. The detecting apparatus moves with the upper die and is mounted in the upper die for limited longitudinal movement in each direction relative thereto. In the preferred embodiment of the invention, the upper die for use with the detecting apparatus comprises three separable parts which are held together by conventional apparatus. Each of the first and second parts have a passageway extending therethrough and the third part has a passageway extending partially therethrough. The longitudinal axes of the passageways are in alignment and are parallel to the longitudinal axis of the upper die but off-set therefrom. 
     The detecting apparatus is mounted in the passageways for movement with the upper die and for longitudinal movement relative to the uppper die. At least portions of the detecting apparatus and at least portions of the passageways have transverse configurations to prevent relative rotational movement between the upper die and the detecting device. The lowermost portion of the detecting apparatus has a transverse configuration corresponding to but slightly smaller than the finger hole in the stay-on-tab so that in normal operation, the lowermost portion of the detecting apparatus will be in its lowermost position when the upper die is in its lowermost position. The detecting apparatus is resiliently urged into its lowermost position. 
     Sensing apparatus is mounted at a fixed location on the upper die for movement therewith. At least a portion of the sensing apparatus and at least a portion of the detecting apparatus are located so that the sensing apparatus will generate a signal when the detecting apparatus is not in its lowermost position when the upper die is in its lowermost position. 
     In the normal operation of the tab wipe down assembly, the lowermost portion of the detecting apparatus will enter the finger hole of the stay-on-tab as the upper die is moving toward its lowermost position. A portion of the tab wipe down assembly will contact a portion of the tab and apply a force thereto a portion of which extends in a lateral direction. However, lateral movement of the pull tab is prevented by contact of the portion of the stay-on-tab surrounding the finger hole and the portion of the detecting apparatus surrounding the lowermost portion. The resilient force acting on the detecting apparatus to urge it toward its lowermost position is of sufficient force to prevent any upward movement of the detecting device resulting from any upward force resulting from the force applied by the wipe down assembly. However, if the stay-on-tab is mis-located, the lowermost portion of the detecting apparatus will contact a portion of the mis-located tab surrounding the finger hole and the lowermost portion of the detecting apparatus will be move upwardly a distance from its lowermost position. Defects other than a mis-located pull tab can also result in upward movement of the detecting apparatus. The sensing apparatus will sense this upward movement and will generate a signal. The resilient force urging the detecting apparatus into its lowermost position is not of sufficient strength to prevent this upward movement of the detecting apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Illustrative and presently preferred embodiments of the invention are illustrated in the drawing in which: 
     FIG. 1 is an illustration of a prior art tab wipe down assembly; 
     FIG. 2 is an elevational view with parts in section of a modification of a portion of the tab wipe down assembly of FIG. 1 in accordance with this invention; 
     FIG. 3 is a top plan view of the finger hole portion of a tab; 
     FIG. 4 is a bottom plan view of a portion of the detecting device of this invention; 
     FIG. 5 is a partial cross-sectional view taken on the line  5 — 5  of FIG. 2; 
     FIG. 6 is a front elevational view of the trigger of this invention; and 
     FIG. 7 is a side elevational view of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, there is illustrated a portion of apparatus for forming a container end with a stay-on-tab and is known as the tab wipe down assembly  2 . The apparatus has a lower die  4  mounted at a fixed location and an upper die  6  mounted for vertical reciprocation along a longitudinal axis. The upper die  6  comprises a first part  8  secured to a ram  10  that is reciprocated by conventional means (not shown). A second part  12  is secured to the first part  8  for movement therewith. The first part  8  has an annular recess  14  formed therein and in which there is located a spring  16 . A third part  18  is secured to the second part  12  for movement therewith. The third part  18  has a die  20  for wiping down the tab ear and another die  22  for holding down the finger hole portion of the stay-on-tab. A sleeve  24  surrounds the second and third parts  12  and  18  and is mounted for reciprocal movement over the second and third parts  12  and  18 . The spring  16  acts on the sleeve  24  to normally urge the sleeve  24  against an annular abutment stop  26 . 
     In FIG. 2, there is illustrated a modification of the first, second and third parts, identified as  8   a ,  12   a  and  18   a , in accordance with this invention. 
     Modified part  8   a  has a passageway  30  extending partially therethrough, a lower surface  32  and a slot  34  cut into the lower surface  32 . A threaded passageway  36  extends from the outer surface of the modified part  8   a  and is in communication with the slot  34 . In different types of wipe down assemblies, the radial location of the slot  34  and the threaded passageway  36  relative to the modified part  12   a , may vary. As explained below, this will have no effect on the operation of the detecting apparatus of this invention. A proximity sensing apparatus  38  is threaded into the threaded passageway  36  and after being adjusted to its proper sensing location is secured in such sensing location by the nut  40 . 
     Modified part  12   a  (illustrated in FIGS. 2 and 5) has a passageway  42  extending therethrough, an upper surface  44  and two slots  46  and  48  cut into the modified part  12   a  through the upper surface  44 . As illustrated, the slots  46  and  48  extend at a substantially right angular relationship but can be of other angular relationships and in some instances may comprise only one slot. The slots  46  and  48  are to accommodate two known variations of the modified part  8   a . In one modification, the slot  46  will be in alignment with the slot  34  and in another modification, the slot  48  will be in alignment with the slot  34 . The passageways  30  and  42  preferably are of a cylindrical configuration but can be of other geometrical configurations. 
     Modified part  18   a  has two passageways  50  and  52  formed therein. The passageway  50  has a transverse cross-sectional area greater than the transverse cross-sectional area of the passageway  52  so as to form an abutment stop  54  therebetween. The passageway  50  preferably is of a cylindrical configuration but can be of other geometrical configurations. The passageway  52  preferably is of a configuration corresponding to but larger than the configuration of the finger hole in a tab as discussed below but can be of other geometrical configurations. The longitudinal axes of the passageways  30 ,  42 ,  50  and  52  preferably are in alignment. 
     The detecting apparatus of this application, as illustrated in FIGS. 2, and  4 - 7 , preferably comprises a trigger  60  and a pilot  62  but may be of other constructions. 
     The trigger  60 , illustrated in FIGS.  2  and  5 - 7 , comprises a first portion  64  preferably having a cylindrical outer surface for longitudinal movement in the passageway  30 ; a second portion  66  preferably having a rectangular configuration and having a section  68  that projects into either of the slots  34  and  46  or the slots  34  and  48 . The section  68  and the slots  34  and  46  or  34  and  48  have planar facing surfaces to guide the longitudinal movement of the trigger  60  and to prevent rotational movement of the trigger  60 . Other structures may be used to prevent relative rotational movement between the trigger  60  and the upper die  2 . The trigger  60  has third and fourth portions  70  and  72  each having a generally cylindrical outer surface for longitudinal movement in the passageway  42 . A fifth portion  74 , integral with the third and fourth portions  70  and  72 , has a reduced outer cylindrical surface so as to reduce the frictional contact between the trigger  60  and the passageway  42 . 
     The pilot  62 , illustrated in FIGS. 2 and 4, comprises a first portion  80  preferably having a cylindrical outer surface for longitudinal movement in the passageway  50 . As illustrated in FIG. 2, the longitudinal extent of the passageway  50  is greater than the longitudinal extent of the first portion  80  to permit the longitudinal movement of the pilot  62 . The pilot  62  has a second portion  82  having a transverse cross-sectional configuration that corresponds to the transverse cross-sectional configuration of the passageway  52  that are of a geometrical configuration so as to prevent rotational movement of the pilot  62  and the upper die  2 . Other structures, such as a key and a keyway, may be used to prevent relative rotational movement between the pilot  62  and the upper die  2 . The transverse cross-sectional area of the first portion  80  is greater than the transverse cross-sectional area of the second portion  82  so as to provide an abutment stop  84 . Also the transverse cross-sectional area of the passageway  50  is greater than the transverse cross-sectional area of the passageway  42  so as to provide an abutment stop  86 . The pilot  62  has a third or lowermost portion  88  which in its lowermost position projects downwardly from the lower surface  90  of the modified third part  18   a . The third or lowermost portion  88  has a transverse cross-sectional configuration that is slightly smaller than the transverse cross-sectional configuration of the finger hole of a tab (described below) so that, in the normal operation of the apparatus, the third or lowermost portion  88  will move through the finger hole of the tab. A resilient spring  90  is located in the passage way  30  and applies a resilient force on the trigger  60  and the pilot  62  to urge them downwardly until the abutment stops  54  and  84  are in a contacting relationship and the third or lowermost portion  88  is in its lowermost position. 
     In FIG. 3, there is illustrated a portion  96  of a pull tab for a container end having a finger hole  98  and a reinforcing portion  100  surrounding the finger hole  98 . The finger hole  98  has a generally linearly extending portion  102  and a generally oval portion  104 . 
     The operation of the apparatus is explaine d below in relation to a mis-located pull tab but as explained above and below other defects can result in preventing the pilot from reaching its lowermost position. The tab wipe down assembly of this invention will function in its conventional manner if the pull tab is not mis-located. That is, the die  20  will function to wipe down the carry strips on the pull tab and the third portion  88  will pass through the finger hole  98  to prevent lateral movement of the pull tab. The spring  90  has a sufficient strength to hold the pilot  62  at its lowermost position so that the abutment stops  54  and  84  are in a contacting relationship 
     The proximity sensing apparatus  38  is adjusted, as described above, to sense the presence of a predetermined amount of the surface  106  of the projecting section  68 . If a stay-on-tab is mis-located, the third portion  88  will not pass through the finger hole  98  and at least a portion of the surface  108  of the third portion  88  will contact at least a portion of the reinforcing portion  100  surrounding the finger hole  98  and this will cause the pilot  62  to move upwardly. The spring  90  does not have sufficient strength to prevent this upward movement of the pilot  62 . The upward movement of the pilot  62  also moves the trigger  60  so that more of the surface  106  is exposed to and sensed by the proximity sensing apparatus  38  which generates a signal indicating a mis-located stay-on-tab. Also, if the stay-on-tab is not mis-located but some foreign object forces the upward movement of the pilot  62 , the trigger  60  will also be moved and the proximity sensing apparatus  38  will generate a signal. The detecting apparatus of this invention can be used to detect defects in the production of any of the container ends having a pull tab secured thereto as illustrated in the Stolle brochure. These defects can result from a mis-located pull tab, a malformed rivet, double container end blanks, scrap in the tab die, scrap in the inserter, dirty vacuum filters, ends below the transfer belt or any other defects that prevents the pilot from reaching its lowermost position. 
     It is contemplated that the inventive concepts herein described may be variously otherwise embodied and it is intended that the appended claims be constructed to include alternative embodiments of the invention except insofar as limited by the prior art.