Abstract:
The present invention relates to an apparatus for capping in succession containers transported on a conveyance device. The apparatus comprises a cap dispensing station for applying caps on the containers. The cap dispensing station includes a cap release passage, a gating unit and a movable cap ejector. The gating unit includes a barrier, capable to acquire either one of first and second operative positions, and a barrier drive mechanism. In the first operative position, the barrier at least partially closes the cap release passage for preventing a cap from freely travelling through the passage under the effect of gravity. In the second operative position, the barrier uncovers the cap release passage for allowing a cap to pass through the passage. The cap ejector engages the barrier drive mechanism such that the barrier drive mechanism causes the barrier to acquire the second operative position. The capping apparatus yields the benefit of repeatable accurate cap dispensing over containers to be capped, by virtue of the novel gating unit.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an apparatus for fitting containers with caps. More particularly, it is directed to a novel capping machine capable to deposit a cap on a container neck such that the cap is aligned with the container neck. 
     BACKGROUND OF THE INVENTION 
     In the bottling industry, reclosable containers are usually sealed with screw-type caps. To achieve a high productivity, the container sealing operation is performed by automatic capping machines processing in succession the containers transported in serial order on a conveyor belt or any other type of materials handling machine. In typical capping machines, the container sealing operation is a two-step process. Firstly, the open container passes underneath a cap dispensing station applying loosely on the container neck a screw-type cap in thread alignment with the threads on the container neck. For the purpose of this specification, the term “thread alignment” designates a condition where the cap is not threadedly engaged on the container neck, however the threads on the cap and on the neck respectively are so disposed that rotation of the cap will cause the threads to mate in the correct fashion, resulting in thread engagement. In contrast, the term “thread misalignment” will be used to identify a condition where rotation of the cap will cause improper thread engagement resulting in a poorly sealed container. The container is then transported to a cap tightening station where a chuck rotatably grips the cap, tightening it and sealing the container. 
     The accurate positioning of the cap on the container neck is an important operation to ensure a proper thread engagement during the cap tightening stage. Existing capping machines use a simple method to deposit the caps on the containers at the cap dispensing station. The caps are fed from a supply chamber or magazine to a cap-dropping aperture where a latch drops the caps on the containers in a timed relationship with the container feed rate. Unfortunately, although a cap is dropped only a very short distance from the top of a container neck, during its free fall the cap may tilt slightly, landing in an improper position on the container and failing to produce the desired thread alignment condition. Deep caps or caps with large threads have inherent self-centering capability and, accordingly, they can compensate, to a certain extent, for an imprecise positioning. However, shallow caps and caps with smaller thread sizes, have little ability to self-center themselves, in which case an improperly positioned cap will fail to produce a correct thread engagement during the cap tightening operation, resulting in a poorly sealed container. 
     In U.S. Pat. No. 5,115,617, issued on May 26, 1992 to H. G. Kalish Inc., a capping machine is disclosed in which the cap dispensing station includes a cap-dropping aperture partially closed by a resilient lip. This lip prevents a cap from travelling through the cap-dropping aperture. The cap dispensing station further includes a selectively actuatable cap ejector that drives the cap through the cap-dropping aperture against the resiliency of the lip, freeing the cap for deposit onto the container neck. Frictional engagement between the resilient lip and the cap during its movement through the cap-dropping aperture guides the cap such that it is precisely positioned on the container. Unfortunately, a weakness of this design is the wear suffered by the resilient lip over time, which causes the opening in the lip to become too large such that the lip can no longer hold a cap properly in place. Further, during movement of the cap through the cap-dropping aperture, the downward motion of the resilient lip may permit a tilting of the cap, resulting in a thread misalignment condition between the cap and the container neck. 
     The background information provided above clearly indicates that there exists a need in the industry to provide an improved mechanism for applying caps onto container necks within capping machines, such that accurate cap positioning is repeatedly achieved. 
     SUMMARY OF THE INVENTION 
     The present invention provides in one aspect an apparatus for capping in succession containers transported on a conveyance device. The apparatus includes a cap dispensing station for applying on each container a cap. The cap dispensing station includes a gating unit that controls the movement of a cap through a cap release passage. When the cap is allowed to travel through the cap release passage it is deposited onto a container underneath. The gating unit includes a barrier associated to the cap release passage, and a barrier drive mechanism associated to the barrier. In a first operative position, the barrier at least partially closes the cap release passage to prevent a cap from freely traveling through the passage under the effect of gravity. In a second operative position, the barrier uncovers the cap release passage to allow a cap to travel through the passage. The apparatus also comprises a movable cap ejector that engages the barrier drive mechanism such that the barrier drive mechanism causes the barrier to acquire the second operative position. 
     The capping apparatus as described above yields the benefit of repeatable accurate cap dispensing over containers to be capped, by virtue of the novel gating unit. 
     In a specific non-limiting example of implementation, the barrier drive mechanism of the gating unit includes a pair of arms slidingly mounted on tracks. The spacial position of the arms is such that they extend in the path of travel of the cap ejector. When the cap ejector moves toward the arms it engages the arms and causes the arms to move on the tracks. The arms are mounted to the barrier such that the movement of the arms causes the barrier to acquire the second operative position in which the cap release passage is uncovered. In particular, the barrier has a pair of portions, each portion mounted to a respective arm. Each barrier portion moves with the respective arm so as to uncover the cap release passage. When the cap has been deposited on the container, the cap ejector is withdrawn. The arms are spring-loaded and they move back to their initial rest position, causing the barrier portions also to move back to the first operative position, at least partially closing the cap release passage to prevent a cap from passing through the passage. 
     In a second broad aspect, the invention provides a capping machine including a cap ejector that can grasp the cap and transport the cap toward the container to be capped. Thus feature is advantageous in that the movement of the cap toward the container is well controlled which translates in a more accurate cap dispensing operation. 
     In a non-limiting example of implementation under the second broad aspect, the cap ejector includes a gripping device that engages and holds the cap, preventing it from moving freely under the effect of gravity. The cap ejector moves toward the container to carry the cap and deposit the cap on the container neck. When the cap ejector has reached the container neck it releases the cap such that the cap rests on the container neck, allowing the cap ejector to withdraw. In a specific non-limiting example of implementation, the gripping device includes a recess at the base of the cap ejector, dimensioned for receiving at least a portion of a cap. A fluid communication channel connected to a source of vacuum terminates in the recess to selectively establish a pressure differential therein. The pressure differential holds the cap in the recess against the force of gravity. The cap ejector then moves toward the container, transporting the cap with it. The pressure differential is terminated once the cap ejector has reached the container, allowing the cap to be released from the cap ejector. 
     In a possible variant, a motor in driving relationship with the cap ejector imparts a rotational movement to the cap ejector for threadedly engaging and tightening the cap on the container neck. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are provided for purposes of illustration only and not as a definition of the boundaries of the invention, for which reference should be made to the appending claims. 
     FIG. 1 is a perspective view of a capping machine constructed in accordance with an example of implementation of the present invention; 
     FIG. 2 is a side elevational view of the machine shown in FIG. 1, some elements being omitted for clarity; 
     FIG. 3 is a top plan view of the machine shown in FIG. 1, some elements being omitted for clarity; 
     FIG. 4 is an enlarged perspective view of the cap dispensing station of the machine shown in FIGS. 1 to  3 ; 
     FIG. 5 is a further enlarged front view of the cap dispensing station shown in FIG. 4; 
     FIGS. 6 to  8  depict the operation of the cap dispensing station; 
     FIG. 9 is an enlarged perspective view of the cap dispensing station, according to a first variant; and 
     FIG. 10 is an enlarged side view of the cap dispensing station, according to a second variant. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1 to  3  illustrate a capping machine  10 , according to a specific non-limiting example of implementation of the present invention. The capping machine  10  includes a conveyor belt  12  that is responsible for transporting in serial order containers  14  that are sealed at a capping assembly  16  and then returned to the conveyor belt  12  for further processing. The capping assembly  16  includes a cap dispensing station  18  loosely applying a cap  20  on the threaded neck of a container  14 , and cap-tightening stations  22  and  24  that pre-tighten and apply the final tightening torque to the caps  20 , respectively. 
     Specific to this example of implementation, the operation of the various stations of the capping assembly  16  is precisely synchronized with the feed-rate of the containers  20  through the machine  10 . Each container  14  is maintained captive during its passage through the various stations of the capping assembly  16  between a stepper wheel  26  rotating in short and essentially uniform angular movements and an arcuate guide rail  28 . The stepper wheel  26  advances each container  14  in discrete steps through the machine  10  precisely positioning the container  14  at the various processing stations. In a particular example, the stepper wheel  26  has double sprocket-like configuration exhibiting a series of container-holding recesses  30  whose shape is selected according to the configuration of the containers  14  to be capped. Power is transmitted to the stepper wheel  26  through a vertically extending shaft  32  from a motor (not shown) housed in a top console  34  also regrouping the various controls of the machine  10 . 
     Screw-type caps  20  are supplied to the machine  10  from a supply chamber  36 . Such a supply chamber  36  is well known to those skilled in the art and accordingly will not be described in further detail. From the supply chamber  36 , the caps  20  are conveyed to the cap dispensing station  18  by sliding under the effect of gravity on a channel  38 . 
     As shown in FIGS. 4 and 5, the cap dispensing station  18  includes a gating unit  40  forming the terminal area of the channel  38 , itself including an aperture  42  for releasing the caps  20  onto the containers  14  passing underneath. This aperture  42  forms, at least in part, a cap release passage  44 . The gating unit  40  controls the movement of a cap  20  through the cap release passage  44 . 
     From a functional point of view, the gating unit  40  includes a barrier and a barrier drive mechanism. The barrier is associated with the cap release passage  44  and may acquire either one of first and second operative positions. In the first operative position, the barrier at least partially closes the cap release passage  44  in order to prevent a cap from freely travelling through the passage  44  under the effect of gravity. In the second operative position, the barrier uncovers the cap release passage  44  in order to allow a cap  20  to travel through the passage  44  onto a container  14  underneath. The barrier drive mechanism is associated with the barrier and causes the barrier to move between the first and second operative positions. 
     Continuing with the example of implementation shown in FIGS. 4 and 5, the gating unit  40  includes a bottom plate  46  that exhibits the aperture  42  and an upstanding U-shaped cap guide  48  whose central curved portion  50  follows peripherally the aperture  42 . Two substantially identical members  52  are mounted to the top surface of the bottom plate  46 , fitting into corresponding slots  56  in the U-shaped cap guide  48 . The members  52  are spring-loaded and slide along tracks  54  of the bottom plate  46 . Each member  52  comprises an arm  58  coupled at its base to a horizontally extending barrier portion  60 , where displacement of an arm  58  causes simultaneous displacement of the respective barrier portion  60 . The springs  62  bias the members  52  such that, at rest, the arms  58  are in a spaced-apart relationship, symmetrically positioned about the vertical axis defined by the center of aperture  42 . Further, the barrier portions  60  extend into and partially close the aperture  42 , preventing a cap  20  from freely travelling through the cap release passage  44  under the effect of gravity. Thus, arms  58  form, at least in part, the barrier drive mechanism of the gating unit  40 , associated with the barrier formed of barrier portions  60 . 
     Note that when the members  52  are at rest, such that the barrier portions  60  extend into the aperture  42 , the barrier portions  60  form a horizontal resting surface for supporting a cap  20  above the cap release passage  44 . 
     Each arm  58  includes an upper wall  64  that, as it progresses downwards towards the base of the arm  58 , angles inward towards the vertical axis. The upper walls  64  of the arms  58  thus form together a tapered cylindrical area. 
     A movable, selectively actuatable cap ejector  66  is provided immediately above the aperture  42 , having a path of travel coinciding with the vertical axis defined by the centerline of the aperture  42 . In a particular, non-limiting example of implementation, the cap ejector  66  includes cylindrical top and bottom portions  68  and  70 , respectively, the top portion  68  being characterized by a wider cross-section diameter than that of the bottom portion  70 . The top  68  and bottom  70  portions are integrally connected by a ramp portion  72  that progressively angles inward towards the vertical axis as it extends downwards from the top portion  68  to the bottom portion  70 . Specifically, the ramp portion  72  of the cap ejector  66  defines a tapered cylindrical portion that is dimensioned to match the tapered cylindrical area formed by the upper walls  64  of the arms  58 . Note that the bottom portion  70  of the cap ejector  66  has a diameter that is substantially equal to the largest diameter of the cap  20 . This diameter is also substantially equal to or smaller than the shortest distance separating the arms  58  of the members  52  at rest. 
     The cap ejector  66  is actuatable to engage the arms  58  of the gating unit  40 , such that the members  52  are displaced and the barrier portions  60  caused to uncover the cap release passage  44 , thus allowing a cap  20  to be deposited on a container  14  located underneath the cap release passage  44 . Further, the cap ejector  66  is responsible for grasping the cap  20  and transporting the cap  20  towards the container  14  to be capped. In a particular example of implementation, the cap ejector  66  includes a gripping device that engages and holds a cap  20  during the movement of the cap  20  through the cap release passage  44 . This gripping device includes a recess  74  for receiving at least a portion of a cap  20 , the recess  74  being terminated within the bottom portion  70  of the cap ejector  66  by a rubber surface  76  for ensuring good contact between the cap  20  and the recess  74 . The walls of the recess  74  surrounding the cap  20  are operative to guide the cap  20  onto the neck of the container  14 . 
     In operation, open containers  14  which have been previously filled with the desired material are transported on the conveyor belt  12 . In the vicinity of the capping assembly  16 , the containers  14  are deflected from their normal course by the stepper wheel  26  guiding and advancing the containers  14  through the various processing stations of the machine  10 . 
     The stepper wheel  26 , turning in uniform angular movements, brings a container  14  immediately below the cap dispensing station  18 , the neck of the container  14  being aligned with the cap release passage  44  defined by the aperture  42 . Screw-type caps  20  to be applied to the containers  14  are fed to the cap dispensing station  18  through the channel  38 . The cap  20  in the most advanced position on the channel  38 , arriving at the gating unit  40 , slides forwardly on the plate  46  and abuts against the curved portion  50  of the U-shaped guide  48 , which positions the cap  20  above the aperture  42 , partially closed by the barrier portions  60  of the members  52  which prevent the cap  20  from dropping on the container  14  underneath. 
     As shown in FIGS. 6 to  8 , the cap ejector  66  is actuated, lowering such that the ramp portion  72  engages the upper walls  64  of the arms  58 . The progressive downward motion of the cap ejector  66  causes the ramp portion  72  to exert a lateral force on the arms  58 , resulting in opposite lateral movement of the members  52 , and thus of the barrier portions  60 , along tracks  54 , away from the vertical axis defined by the center of the aperture  42 . As the barrier portions  60  are displaced, they progressively uncover the cap release passage  44 . 
     The ramp portion  72  of the cap ejector  66  is positioned a specific distance X from the base of the cap ejector  66  in order to ensure that, during actuation of the cap ejector  66 , the cap release passage  44  is completely uncovered by the barrier portions  60  prior to the moment at which the base of the cap ejector  66  reaches the top surface of the bottom plate  46 . Further, the distance X is calculated such that the recess  74  of the cap ejector  66  has received at least a portion of the cap  20  prior to the moment at which the barrier portions  60  completely uncover the cap release passage  44 , such that the cap  20  is grasped by the recess  74  during its travel onto the container  14  underneath. 
     Note that in an alternative example of implementation, the members  52  may be pivotally mounted to the dispensing unit  40 . In operation, the cap ejector  66  would be actuated to engage the arms  58  of the gating unit  40 , the continuous downward motion of the cap ejector  66  causing a pivotal movement of the arms  58  with respect to the gating unit  40 . This pivotal movement of the arms  58  would cause displacement of the barrier portions  60  in a direction such as to uncover the cap release passage  44 . 
     Thus, once the cap release passage  44  has been completely uncovered, the cap  20  and cap ejector  66  (the cap  20  being contained within the recess  74  of the cap ejector  66 ) travel through the cap release passage  44  towards the container  14  underneath. During the downward motion of the cap  20 , through the cap release passage  44  and onto the container  14 , the walls of the recess  74  in the cap ejector  66  are operative to prevent the cap  20  from moving sideways or tilting, effectively achieving a guiding function during the cap  20  downward travel distance. To complete the cap dispensing cycle, once the cap  20  has been deposited on the container  14  neck, the cap ejector  66  is retracted, back up through the cap release passage  44  to its initial position. In accordance with the removal of the cap ejector  66 , the members  52  of the gating unit  40  are biased by the springs  62  back to their initial, rest position, such that the barrier portions  60  once again extend into and at least partially close the cap release passage  44 . Thus, a subsequent cap  20  may enter the gating unit  40  and be positioned above the aperture  42 , prevented from descending therethrough onto a container  14  underneath by the barrier portions  60 . 
     In order for this guiding function to be achieved throughout the downward motion of the cap  20 , such that a proper alignment condition is achieved between the cap  20  and the container  14  neck, the distance between the top edge of the container  14  neck and the bottom surface of the plate  46  must be equal to the cap height. Before each production run, the distance from container  14  to bottom surface of plate  46  must be set according to the dimensions of the containers and cap to be processed. 
     It should be appreciated that the cap ejector  66  and the members  52 , in combination, form a latch system to control the cap release onto the containers  14 . This latch system is extremely effective while remaining mechanically simple and generally impervious to wear by repeated use. 
     The structure of the gating unit  40  will depend on the configuration of the cap  20  that is to be dispensed. Due to the simplicity of this component, various dispensing units may be easily fabricated to suit different cap shapes and sizes so as to render the machine versatile for use in applying screw-type caps of different kinds. However, each gating unit  40  will be provided with the necessary tracks and slots to receive the members  52 . 
     Simultaneous with the retraction of the cap ejector  66  at the completion of the cap dispensing cycle, the stepper wheel  26  is advanced to bring the container  14  in a position for engagement by the first tightening station  22  where the cap  20  is partially tightened. The wheel  26  is then revolved again to bring the container  14  to the second tightening station  24  where the final tightening torque is applied to the cap  20 . The structure and operation of the tightening stations  22  and  24  will not be described in further detail because they are well known to those skilled in the art. 
     In an alternative, non-limiting example of implementation, an air motor  78 , in driving relationship with the cap ejector  66 , imparts a rotational movement to the cap ejector  66 , as shown in FIG.  9 . Flexible compressed air supply lines  80  are connected to the motor  78  to supply driving fluid thereto at various vertical positions of the motor. In operation, when the cap ejector  66  is actuated to eject a cap  20  from the cap release passage  44 , a continuous rotational movement is imparted to the cap  20  by the cap ejector  66  when the cap  20 , contained at least partially within the recess  74  of the cap ejector  66 , has cleared the aperture  42  and is being deposited on the container  14  neck. The rotational movement imparted to the cap  20  during its deposit on the container  14  causes the cap  20  to be threadedly engaged on the container  14  neck. Accordingly, the cap  20  may be both deposited and subsequently tightened on the container  14  neck by the cap ejector  66 , potentially removing the requirement for one or both tightening stations  22  and  24 . Note that, in this example of implementation, the recess  74  of the cap ejector  66  is sized to receive a cap  20  such that the cap  20  extends slightly from the base of the cap ejector  66 , to allow for tightening of the cap  20  onto the container  14  neck. 
     As shown in FIG. 10, in yet another alternative, non-limiting example of implementation, the gripping device of the cap ejector  66  includes a fluid communication channel  82 . The fluid communication channel is coupled at one end to a vacuum unit  84  and, at the other end, terminates in the recess  74 . The vacuum unit  84  selectively establishes an air pressure differential in the recess  74 , for maintaining the cap  20  in the recess  74 . This air pressure differential holds the cap  20  in the recess  74  of the cap ejector  66 , against the force of gravity, during deposit of the cap  20  onto the container  14  neck. The air pressure differential is terminated once the cap ejector  66  has reached the container  14  and the cap  20  is supported by the container  14 , allowing the cap  20  to be released from the cap ejector  66 . The rubber surface  76  of the recess  74  ensures good contact between the cap  20  and the fluid communication channel  82 , such that the air pressure differential established by the vacuum unit  84  is properly applied to the cap  20  within the recess  74 . 
     An advantage provided by this particular example of implementation is that the distance between the top edge of the container  14  neck and the bottom surface of the plate  46  may be greater than the cap height, since the air pressure differential established by the vacuum unit  84  ensures that the cap  20  is held within the recess  74  of the cap ejector  66  during the entire downward deposit motion. Note that the fluid communication channel  82  may include a valve, not shown, for controlling the flow of air within the channel  82 . 
     Note that in an alternative embodiment of the present invention, the caps  20  are snap-type caps (no threads), where a container  14  is sealed with a snap-type cap  20  by simply snapping the cap  20  onto the neck of the container  14 . The above examples of implementation of the capping machine  10  apply equally to snap-type caps. It should be noted that in the case of snap-type caps, the capping machine  10  may exclude the tightening stations  22  and  24  (for tightening screw-type caps  20  onto containers  14 ), as well as the air motor  78  (for imparting a rotational movement to the cap ejector  66 ). 
     The above detailed description should not be interpreted in any limiting manner as refinements and variations can be made without departing from the spirit of the invention. The scope of the invention is defined in the appended claims and their equivalents.