Abstract:
To provide a pin tip attachment structure that can engage a container with a bottom, such as a can or bottle, and convey the container without scratching it, a small diameter portion having a predetermined length is formed at a front end portion of a pin. A bushing is fitted in a lower end portion of a cylindrical hole of a pin tip having the cylindrical hole opened at a lower end side, and the bushing is vertically movably inserted onto the small diameter portion of the pin. A stopper portion for retaining the bushing is provided at a front end of the small diameter portion. A spring receiver portion is provided below the small diameter portion, and a coil spring is provided in a compressible manner between the spring receiver portion and the bushing or the lower end of the pin tip.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a structure for stretching a pin of a chain and attaching a pin tip to an end of the pin, the chain being for engaging and conveying a container with a bottom, such as a can or bottle. 
     2. Related Art 
     Recently, aluminum or steel cans have been often used for containers of drinks such as beer or juice. A large number of the cans are manufactured and bottled with drinks in factories. When the cans are manufactured, many steps such as a step of printing on an outer circumferential face, a step of drying, and a step of coating the inside are necessary. In each of the steps, the cans are conveyed by a pin chain conveyor.  FIG. 9  shows aluminum cans  102  being conveyed while being engaged by pin tips  101  of a pin chain conveyor  100 . Of course, steel cans are conveyed in the same way. 
     Speed of the aluminum cans  102  being conveyed while being engaged by the pin tips  101  of the pin chain conveyor  100  is extremely fast, about 200 m/min. Therefore, since the aluminum cans  102  engaged by the pin tips  101  are moving without rest, scratches are induced on the insides of the cans by rubbing of the cans with the pin tips  101 . The scratches cause imperfect coating of the inside of the aluminum cans. As a result, corrosion is induced by bottled drinks, resulting in reduction in quality of the drinks bottled in the aluminum cans  102 . 
     The “pin chain conveyor” disclosed in JP-A-7-149417 is configured to be able to prevent deformation of an open edge of a can. That is, a pin chain conveyor has a chain to be conveyed, pins projecting from the chain, pin tips to be attached to ends of the pins, the pin tips being reversely covered with cylinders having bottoms and having cylindrical outsides; wherein the pin tips are longer than the height of the cylinders having bottoms, and end portions at a chain side of the pin tips are formed in a taper shape having a tapered end. However, while the open edges of the cylinders engaged by such pin tips are not deformed while being conveyed, scratches cannot be prevented from being induced on the inside. 
       FIGS. 10A to 10C  show a conventional attachment structure of a pin tip attached to a pin. A pin tip  104  shown in  FIG. 10A  has a small outer diameter size, and is directly pressed to fit with a pin  103 . In some cases, a retention process is performed to prevent separation of the pin tip  104  from the pin  103 . 
     A pin tip  105  shown in  FIG. 10B  has a reverse truncated cone shape, and is set on a coil spring  107  which is set on and supported by a ring plate  106  attached to the pin  103 . A fixing tool  108  is attached to a front end of a pin such that the pin tip  105  is not separated from the pin  103 . Accordingly, the pin tip  105  can be lowered while compressing the coil spring  107  when load is exerted from above, so that the aluminum can  102  being conveyed can be supported and conveyed without receiving an impact. 
     An attachment structure of a pin tip  109  shown in  FIG. 10   c  is similar to that of  FIG. 10B , except that the coil spring  107  and the ring plate  106 , which support the pin tip  109 , are configured to be accommodated in a recess formed at a lower end portion of the pin tip  109 . Therefore, the structure has an appearance that the coil spring  107  and the ring plate  106  are not exposed outside of the pin tip  9 . 
     If the pin tips  105  and  109  are supported by the coil spring  107  as shown in  FIGS. 10B and 10C , when load is exerted, the coil spring  107  is compressed and deformed so that the pin tips  105  and  109  can slide and move downward along the pin  103 , which prevents scratches from being induced on the inside of the aluminum can  102  being conveyed. However, such an attachment structure cannot be used for the pin tip  104  having a small size as shown in  FIG. 10A . Therefore, there has been a difficulty that the large pin tip  105  or  109  as shown in  FIG. 10B  or  10 C cannot be used for conveying a bottle or can having a small port, and consequently impact force is exerted between the pin tip and the aluminum can  102  being conveyed, causing scratches on the inside of the can. 
     SUMMARY OF THE INVENTION 
     It is desirable to provide a pin tip attachment structure of a chain for can making, which can support a pin tip via a coil spring even if the pin tip is a small pin tip that can support a container having a small port. 
     Thus, a pin tip attachment structure according to an embodiment of the invention is in a configuration where a small diameter portion having a predetermined length is formed at an end portion of a pin; a bushing is provided, the bushing being fitted in a lower end portion of a cylindrical hole of a pin tip having the cylindrical hole opened at a lower end side, and vertically movably inserted on the small diameter portion; a stopper stopper portion for retaining the bushing is provided at a front end of the small diameter portion; a spring receiver portion is provided below the small diameter portion; and a coil spring is provided in a compressible manner between the spring receiver portion and the bushing or the lower end of a pin tip. 
     According to such a configuration, since the pin tip is supported by the coil spring, and can be vertically moved with expansion and contraction of the coil spring within a range of the small diameter portion of the pin, when an upper end of the pin tip is pressed, the coil spring is compressed and is lowered. At that time, the bushing slides with the small diameter portion as a guide. Here, it is preferable that the cylindrical hole of the pin tip is made to have a step, and the lower end portion of the hole, which is to be fitted with the bushing, is made to have a slightly large diameter, and an upper side of the hole is made to have a smaller diameter for vertical movement of the stopper portion at a front end of the pin. 
     The bushing is preferably a bushing with a collar portion at a lower end because it is easily attached to the pin tip. Moreover, when a slit groove is formed in the bushing in a longitudinal direction so that inner diameter of a hole of the bushing can be expanded, even if the stopper portion is fixed, the bushing can override the stopper portion and can be inserted onto the small diameter portion of the pin. 
     The spring receiver portion can be a ring plate attached to the periphery of the pin, or may be formed by forming a receiver base using a step on the periphery of the pin. 
     The stopper portion can be formed by press fitting and fixing of a sleeve with respect to the pin, or can be formed by forming a screw thread at the front end of the pin and then screwing a nut with the thread. According to such a configuration, the stopper portion can be attached to the front end of the pin after attaching the bushing irrespective of a shape of the bush, and therefore assembly operation is facilitated. 
     The stopper portion may be a large diameter portion integrally formed with the pin, and in this case, a bushing having a slit groove formed in a longitudinal direction is used. 
     According to the pin tip attachment structure of the invention, since the pin tip can be supported while being set on the coil spring even if the pin tip is small, when a container is engaged by the pin tip, the coil spring is compressed and deformed and consequently an impact is mitigated even if the container has a small port, which eliminates scratches induced on the inside of a can or bottle. 
     On the other hand, for a can or bottle, it is extremely important to avoid adhesion of oils and fats because the can or bottle will contain drinks, and also when the oils and fats are adhered on the inside of the can or bottle, coating performance of paint becomes worse. However, the pin tip attachment structure of the invention is configured such that the pin is attached with the coil spring or the bushing, and the pin tip can be finally attached. Accordingly, the structure of the invention is advantageous in that the possibility of adhesion of oils and fats to the pin tip is extremely reduced, and consequently adhesion of oils and fats to the inside of a can or bottle is suppressed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  show vertical section views of a pin tip attachment structure according to a first embodiment of the invention, which represent a case that a pin tip is in a raised position and a case that it is in a lowered position respectively; 
         FIGS. 2A ,  2 B and  2 C show vertical section views of a front-end portion of a pin to be attached with a pin tip in the structure, and a condition where a coil spring is attached to the end portion and a condition where a bushing with collar is attached to the end portion, respectively; 
         FIGS. 3A and 3B  show a front view and a plan view of the bushing with collar, respectively; 
         FIGS. 4A and 4B  show vertical section views of a pin tip attachment structure according to a second embodiment of the invention, which represent a case that a pin tip is in a raised position and a case that it is in a lowered position respectively; 
         FIGS. 5A and 5B  show vertical section views of a pin tip attachment structure according to a third embodiment of the invention, which represent a case that a pin tip is in a raised position and a case that it is in a lowered position respectively; 
         FIGS. 6A and 6B  show vertical section views of a pin tip attachment structure according to a fourth embodiment of the invention, which represent a case that a pin tip is in a raised position and a case that it is in a lowered position respectively; 
         FIGS. 7A ,  7 B and  7 C show vertical section views of a different embodiment of the front end portion of the pin, which represent the front end portion of the pin to be attached with a pin tip, a condition where a coil spring is attached to the front end portion, and a condition where a bushing with collar is attached to the front end portion, respectively; 
         FIGS. 8A and 8B  show plan views of a condition where the pin tip seizes an aluminum can, and a condition where it seizes an aluminum bottle, using partial cross sections, respectively; 
         FIG. 9  shows a schematic plan view of a pin chain conveyor; and 
         FIGS. 10A ,  10 B and  10 C show plan views of conventional pin tip attachment structures. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1A and 1B  show a pin tip attachment structure according to a first embodiment of the invention, in which a reference  1  indicates a pin tip, reference  2  indicates a coil spring, reference  3  indicates a pin, reference  4  indicates a bushing with collar, and reference  5  indicates a ring plate, respectively. The pin tip  1  is attached to the pin  3  in a stretchable and contractible manner by the coil spring  2  mounted on the pin  3 .  FIG. 1A  shows a case that the coil spring  2  is stretched and the pin tip  1  is therefore in a raised (or extended) position, and  FIG. 1B  shows a case that the coil spring  2  is compressed and deformed and the pin tip  1  is therefore in a lowered (or contracted) position. 
     The pin tip  1  has a front end side formed in a semispherical shape, and has a cylindrical hole  1   a  opened at a lower end side in which the bushing  4  is fitted. At a front end portion  6  of the pin  3 , a thinned small-diameter portion  7  is formed, and a large diameter portion  8  having the same size as size of the pin  3  is integrally formed with a front end of the pin, as shown in  FIG. 2A . The ring plate  5  is attached to a lower side of the small-diameter portion  7 , and as shown in  FIG. 2B , the coil spring  2  is fitted over the front-end portion  6  of the pin and set on the ring plate  5 . Then, as shown in  FIG. 2C , the bushing  4  is attached with and retained by the large diameter portion  8  at the front end of the pin. 
     As shown in  FIGS. 3A and 3B , the bushing  4  is in a configuration where a slit groove  9  is formed in a longitudinal direction, so that the inner diameter “d” of the bushing can be expanded. In the bushing  4 , a collar portion  11  is formed at a lower end of a cylindrical bushing portion  10 , and a hole  12  is formed in an axial direction through the center. To fit the bushing is on the pin  3 , first, the large diameter portion  8  of the front end of the pin  3  is inserted into the hole  12 , and at that time, the slit groove  9  is expanded by the large diameter portion  8  of the pin, such that the inner diameter “d” of the hole  12  is expanded to be at least the outer diameter “D” of the large diameter portion  8  of the pin (refer to  FIG. 2B ) and the bushing is fit on the large diameter portion  8 . 
     Next, when the bushing  4  engaged with the large diameter portion  8  is further pushed down, the bushing  4  is inserted over the small diameter portion  7  in the manner shown in  FIG. 2C . At that time, the slit groove  9  that has been expanded by the large diameter portion  8  is returned to have an original width so that the inner diameter “d” of the bushing  4  becomes smaller than the outer diameter “D” of the large diameter portion  8 . Then, the coil spring  2  is pinched between the ring plate  5  and the collar portion  11  and thus compressed. Therefore, the bushing  4  is urged upward at all times by the coil spring  2 , and an upper end  13  of the bushing is seized against a lower end of the large diameter portion  8  of the pin. The bushing  4  that has been pushed down and fitted over the small diameter portion  7  is not disengaged because the inner diameter “D” of the hole  12  is smaller than the outer diameter “D” of the large diameter portion of the front end of the pin. 
     The bushing  4  fitted with the pin  3  in this way is fitted into a lower end of a cylindrical hole  1   a  of the pin tip  1 , such that the pin tip  1  is attached to the pin  3  ( FIG. 1A ). Then, when the pin tip  1  is pressed, the coil spring  2  is compressed and deformed, such that the pin tip  1  is lowered, and the collar portion  11  of the bushing  4  is contacted against a base  14  using a step formed at a lower side of the small diameter portion  7  of the pin  3 , such that the pin tip  1  is stopped (refer to  FIG. 1B ). When pressing force is released, the coil spring  2  is expanded and the pin tip  1  is raised as shown in  FIG. 1A . 
       FIGS. 4A and 4B  show a pin tip attachment structure according to a second embodiment of the invention. While the basic structure is the same as the first embodiment, the pin  3  does not have the ring plate  5 . Instead, a receiver base  18  for receiving the coil spring  2  is formed on the pin  3 , and the coil spring  2  rests on the receiver base  18 , and elastically supports the pin tip  1 .  FIG. 4A  shows a case that the coil spring  2  is extended and thus the pin tip  1  is in a raised position, and  FIG. 4B  shows a case that the coil spring  2  is compressed and deformed and thus the pin tip  1  is in a lowered position. 
       FIGS. 5A and 5B  show a pin tip attachment structure according to a third embodiment of the invention. While a basic structure is the same as in the case of the first embodiment, the structure is different in that the bushing  4  is configured by separate pieces including a bushing part and a collar part. That is, the bushing  4  is configured with a lower end of the bushing part fitted in a concave portion provided in a top of the collar part.  FIG. 5A  shows a case that the coil spring  2  is extended and thus the pin tip  1  is in a raised position, and  FIG. 5B  shows a case that the coil spring  2  is compressed and deformed and thus the pin tip  1  is in a lowered position. 
       FIGS. 6A and 6B  show a pin tip attachment structure according to a fourth embodiment of the invention. While the basic structure is the same as the first embodiment, the structure is different in that a bushing  19  to be fitted into the hole of the pin tip  1  is configured to have only the bushing part without a collar part. Here, the upper end of the coil spring  2  directly contacts against the lower end of the pin tip  1  to support the pin tip  1 .  FIG. 6A  shows a case that the coil spring  2  is extended and thus the pin tip  1  is in a raised position, and  FIG. 6B  shows a case that the coil spring  2  is compressed and deformed and thus the pin tip  1  is in a lowered position. 
     As shown in  FIGS. 7A to 7C , the pin  3  can be attached with a sleeve configured by a separate component, without having the large diameter portion  8  (refer to  FIG. 2A ) integrally formed at the front-end portion. That is, as shown in  FIG. 7A , the large diameter portion is not integrally formed at the front end of the pin, and a small diameter portion  7  extending to the front end is formed; and the coil spring  2  is set on the ring plate  5  attached to a lower side of the small diameter portion  7 , and the bushing  4  is set on the coil spring  2  ( FIG. 7B ); then the bushing  4  is pushed down to compress and deform the coil spring  2 , so that a sleeve  15  is pressed and fitted on the front end of the small diameter portion  7  ( FIG. 7C ). Here, the outer diameter of the sleeve  15  is made to be the same as outer diameter of the large diameter portion  8 , so that the upper end  13  of the bushing  4  contacts against a lower end of the sleeve  15  for retention. By using such a configuration, the bushing  4  need not have the slit groove. 
     It is obvious that the outer diameter of the sleeve  15  need not be made to be the same as the outer diameter of the large diameter portion  8 , so long as it is larger than the inner diameter “d” of the hole  12  of the bushing  4 . The bushing  4 , which is configured so that it does not disengage from the pin after press fitting of the sleeve  15 , is then attached with the pin tip  1 , resulting in the same configuration as in the first embodiment. Alliteratively, instead of the sleeve  15 , a nut may be screwed onto the pin. That is, when a screw thread portion is formed on the front end of the small diameter portion  7 , and the nut is screwed onto the screw thread portion, the bushing  4  contacts against the nut and thus is not disengaged. 
       FIG. 8A  shows a case that one aluminum can  16  is engaged by a pin tip  1   a , and  FIG. 8B  shows a case that one aluminum bottle  17  is engaged by a pin tip  1   b . The pin tip attachment structure of an embodiment of the invention can be used for conveying a container in a shape having a small port such as the aluminum bottle  17  shown in  FIG. 8B , since the structure is configured to be usable even in the case that the pin tip  1  has a small diameter. However, the pin tip  1   a  having a large diameter as shown in  FIG. 8A  can be obviously attached by using the same structure.