Abstract:
A capping head assembly has a first housing with a spindle mounting collar and supports a clutch housing. The clutch housing has an upper portion with a first magnetic ring and a lower portion with a second magnetic ring. The lower portion is freely rotatable relative to the upper portion and permits the adjustment of the air gap between the first and second magnetic rings. A locking mechanism maintains the adjusted air gap at a selected value that represents a definable torque level in the magnetic clutch. The capping head also includes a post assembly calibration system that establishes a known reference point, which compensates for manufacturing tolerances between individual capping heads.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/092,132, filed Jul. 9, 1998. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a screw capping head with a magnetic clutch for applying pre-threaded closures onto threaded containers. More particularly, the invention provides a capping head with torque adjustment features. 
     BACKGROUND OF THE INVENTION 
     Capping machines for the application of prethreaded closures onto prethreaded containers have been known for some time. In order to ensure that a prethreaded closure is not applied too tightly, which could possibly result in damage, conventional screw capping machines are provided with a screw capping head often called a “headset” having a torque dependent clutch. The clutch limits the maximum torque which can be transmitted to the prethreaded closure. Clutches of various types have been used. These have included slipping clutches and mechanical torque limiting clutches and also magnetic clutches. One example of a magnetic clutch is shown in U.S. Pat. No. 5,490,369 to Ellis et al., which is assigned to the Aluminum Company of America and which in incorporated herein by reference. Other examples of clutches are disclosed in U.S. Pat. Nos. 4,364,218; 4,492,068; 4,674,264; and 5,197,258. While many prior types of clutches have been generally satisfactory, many have not adapted themselves to ready adjustability, thus resulting in substantial down time when changes in the amount of applied torque are required due to different closures being applied, application forces required, etc. The Ellis et al., U.S. Pat. No. 5,490,369 teaches a capping head with an adjustable magnetic clutch consisting of opposed rings of magnet. One of the rings is disposed in a piston ring assembly that is adjustable relative to the other magnetic ring in order to vary the torque limit of the clutch. 
     SUMMARY OF THE INVENTION 
     Briefly, the screw capping head of this invention relates to a head assembly for applying prethreaded closures onto prethreaded containers which provides for readily changing the torque to be applied to the various closures, thus making the capping head adaptable to be used with a variety of different closures and containers. 
     A capping head incorporating the instant invention includes a first housing assembly adapted to be secured to a rotatable drive spindle. A clutch housing is mounted onto the first housing assembly and adapted for axial movement relative to the housing. The clutch assembly has an upper portion and a lower portion. The upper portion includes a magnetic clutch comprising a first circular ring of magnets secured to the portion of the clutch to which the drive spindle is connected. A clutch lower housing portion is in axial alignment with and mounted for free rotation relative to the clutch housing upper portion. The clutch housing lower portion comprises a second ring of magnets axially spaced from the first ring of magnets, which are mounted in the clutch housing upper portion. Together, the first and second rings of magnets define a magnetic clutch. The gap between these axially spaced sets of magnets determines the torque to be applied to the closure. The clutch is capable of slipping after the application of a prethreaded closure onto a prethreaded container when the desired torque value has been reached or exceeded. Essentially, the mode of operation is that as the chuck engages the cap upon the container to be capped, a top load is provided for cap-to-container sealing and/or for adequate rotary frictional engagement between the chuck and the cap by slight telescoping of the spindle and housing to compress a spring disposed therebetween. The magnetic attraction between the magnetic rings will impart at torque load from the housing which rotates with the drive spindle with the chuck assembly. This torque load permits the chuck assembly to engage and tighten the cap which has previously been threadedly engaged onto a container to a predeterminable tightness beyond which the mechanical resistance to further tightening overcomes the magnetic attraction. When this occurs, the magnetic clutch assembly merely slips as the spindle and associated housing continue to rotate with respect to the clutch lower housing portion. 
     The magnetic clutch assembly of the instant invention provides a mechanism for the calibration of the magnetic torque load to any number of predetermined set positions. Additionally, once a predetermined set position is established such as after the manufacture of the clutch assembly, the actual torque of the magnetic clutch can be adjusted through a range of values from, for example, a magnetic torque of 7.0 inch pounds to 22.5 inch pounds, by means of a predetermined set of incremental adjustments. These adjustments are possible through the use of an adjusting ring that permits the selected change of the torque value from a first predetermined value to a second (or different) predetermined value. Furthermore, the nature of the adjusting ring permits the return from the second predetermined value to the first predetermined value through a simple incremental movement of the adjustment ring. 
     Therefore, in summary, a capping head assembly comprises a first housing having a spindle mounting collar means and means for supporting a clutch housing. The clutch housing has an upper portion with a first magnetic ring means and a lower portion with a second magnetic ring. The lower portion is freely rotatable relative to the upper portion of the clutch housing. The lower portion includes means for establishing an adjustable air gap between the first and second magnetic rings. Locking means maintain the means for adjusting an air gap at a selected position. 
     It is therefore an object of this invention to provide an improved capping head with a magnetic clutch that permits the selection of a torque load. 
     It is a further object of this invention to provide a capping head with a magnetic clutch that can be calibrated during assembly to compensate for manufacturing tolerances that might cause the magnetically driven torque forces to vary from unit to unit. 
     It is yet another object of this invention to provide a capping head with a structure that facilitates the wash down or cleaning of the capper head and associated support equipment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above as well as other features and advantages of this invention can be more fully appreciated through consideration of the detailed description of the preferred embodiment in conjunction with the accompanying drawings in which: 
     FIG. 1 is a cross sectional view of a capping head embodying the present invention; 
     FIG. 2 is a cross sectional view of an alternative embodiment of the capping head of this invention; 
     FIGS. 3A through 3G is a view generally taken along lines  3 — 3  of FIG. 1 illustrating in an exploded view, the clutch housing lower portion and sections therethrough; 
     FIG. 4 is a detailed view of the clutch portion of the capping head assembly; 
     FIG. 5 is a detailed view of the torque adjustment controls in a locked position; and 
     FIG. 6 is a detailed view of the torque adjustment controls in an open position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIGS. 1 and 2, there are shown alternative embodiments of the instant invention. The primary difference between these two embodiments is the location of the top load spring. As will be appreciated through the detailed description below, in FIG. 1, the top load spring is externally mounted relative to the spindle mounting collar and the upper portion of the clutch assembly housing. In FIG. 2, the top load spring is mounted internally relative to the spindle mounting collar and the upper portion of the clutch housing. In both drawings, like elements will be identified with like reference characters. Those specific elements whose structures are modified to accommodate the internal or external disposition of the top load spring will be identified with reference characters denoted as ‘I’ for internal and ‘E’ for external. 
     Referring now specifically to FIG. 1, a screw capping head assembly is generally indicated by the reference character  10 . The assembly is designed to be attached by means of its spindle mounting collar  12  to a drive means that is not shown. It is common for a screw capping machine to be driven by a turret assembly having eight, ten, or more such screw capping heads as at described herein positioned in a circular fashion about a turret. Each capping head reciprocates up and down so as to move into alignment with a container that is to be sealed with a prethreaded closure. The screw capping head assembly  10  incorporates an upper housing  14  of which the spindle mounting collar  12  is one component, a clutch housing  16  comprising an upper portion  18  and a lower portion  20 , and chuck assembly  22 . 
     The upper housing  14  includes an adapter housing  24  with radially inwardly projecting splines  26 . The spindle mounting collar  12  is mounted onto the adapter housing  24  by means of fastening screws  28 . An axially disposed knockout rod  30  extends through an inner chamber  32  defined by the upper housing  14 . The knockout rod  30  is spring biased by spring means  34  so as to be retained in a generally retracted position relative to the chuck  22 . In operation, the knockout rod  30  is actuated by a cam system in the turret housing. 
     The clutch housing  16  has an upper portion  18  that includes radially outwardly extending splines  36  which cooperate with the splines  26  of the upper housing  14  to permit the axially displacement of the clutch housing  16  relative to the upper housing  14 . The external top load spring  38 E tends to bias the clutch housing  16  away from the upper housing  14 . However, the clutch housing  16  is retained within the upper housing  14  by a radially extending shoulder portion  40  of the splined portion of the upper clutch housing that engages a corresponding should portion  42  in the spindle mounting collar. This configuration permits the clutch housing  16  to be compressed from a maximum extended position relative to the spindle mounting collar during the application of threaded closures to containers. As the assembly is rotated through the mounting of the spindle mounting collar onto a turret system, the rotation of the upper housing is transmitted to the clutch housing through the interconnected splines of the clutch housing and the upper housing. 
     As shown in FIG. 2, the internal top load spring is indicated by reference character  38 I and is circumferentially disposed about the portion of the upper housing  14  defining the chamber  32 . Internal spring  38 I rests on an internal flange  44  of the spindle mounting collar  12 . 
     Considering FIGS. 1 through 4, it can be seen that the clutch housing  16  includes an upper portion  18  and a lower portion  20 . The lower portion  20  is supported by bearing means  48  so as to be freely rotatable relative to the upper portion  16  of the clutch housing  16 . The external race  50  of the bearing means  48  is securely retained within the upper portion  18  of the clutch housing and the inner race  52  is retained by the lower portion  16  of the clutch housing. The rotational movement of the upper portion of the clutch housing is transmitted to the lower portion of the clutch housing by means of the magnetic clutch generally indicated by the reference character  54 . The magnetic clutch  54  operates without contact, it is not affected by wear or by warming. Power transmission takes place via two magnet rings  56  and  58 . The magnetic rings  56  and  58  are disposed one above the other in axial alignment. The bottom most magnetic ring or lower magnetic ring  56  is retained in a fixed position with respect to the upper portion  18  of the clutch housing. As will be described below, this magnetic ring includes an adjustment feature that allows the magnetic clutch  54  to be “zeroed” after final assembly of the capping head so as to permit the accurate adjustment of the magnetic clutch through a series of predetermined values. 
     The lower portion  20  of the clutch housing  16  is mounted by means of bearings  48  for free rotation relative to the clutch housing upper portion  16 . As best viewed in FIG. 3, the clutch housing lower portion includes three primary elements: a first member  60  that is mounted for rotation in a fixed axial position relative to the clutch housing upper portion  18 , a second member  62  axially displaceable relative to the first member  60  and locking means  64  for maintaining the second member  62  in a predetermined axially displaced position with respect to the first member  60 . The upper magnetic ring  58  is mounted in a radially extending shoulder portion  66  of the second member  62 . The first member  60  includes an upper threaded portion  68  and a lower splined portion  70 . The second member  62  has internal threads  72  which engage the threaded portion  68  of the first member  60 . As the second member  62  is rotated about its threaded portion, it travels axially with respect to the fixed location of the first member  60 . The rotation of the second member  62  with respect to the first member  60  causes the upper magnetic ring  58  to approach or withdraw with respect to the lower magnetic ring  56 . This travel toward and away from the lower fixed magnetic ring changes the air gap between the magnetic rings. The adjacent rings of magnets define the magnetic clutch and thus, as is well known by those skilled in the art, the transmittable torque between the clutch housing upper portion  18  and the clutch housing lower portion  20  is determined by the gap between the magnetic rings  56  and  58 . Thus, when the magnets are closer together, there is a greater torque transmitted between the upper housing  14  with the upper portion of the clutch assembly  16  and the lower portion  20  of the clutch assembly. And, conversely, when the magnets of the rings  56  and  58  are spaced further apart, the torque is reduced. Generally speaking, the gap between the magnetic rings will vary between about 0.34 mm to 0.90 mm, which will provide a torque limit variation between 22.5 and 7.0 inch pounds respectively. The locking means  64  comprises a collar  74  that includes radially internally projecting splines  76  and axially upwardly extending teeth  78 . The splines  76  of the collar  74  cooperate with the splined portion  70  of the first member  60 . This cooperation facilitates the axial displacement of the collar  74  with respect to the second member  62 . The second member  62  includes downwardly and axially projecting locking teeth  80  which cooperate with the upwardly extending teeth  78  of the locking means collar  74 . When in its uppermost locked position, the locking means  76  prohibits the rotation of the second member  62  relative to the first member  60 . When the collar  74  is axially distanced from the second member  62  so that the teeth  78  of the collar  74  and the locking teeth  80  of the second member  62  are not engaged, the second member  62  is rotatable relative to the first member  60  by means of the threaded portion  68 . The locking means collar  74  may be retained in a locked position by means of a set screw  82  (see FIGS. 5 and 6) or by means of a magnetic ring  84  that biases the locking means in a closed, locking position relative to the second member  62 . Preferably, the second member  62  may be rotated approximately 360° about the first member  60 . This 360° rotation provides an optimum range of magnetic torque by moving the upper magnetic ring toward or away from the lower magnetic ring. The teeth  80  may be marked with indicia representing the several predetermined torque values. The adjustment ring  84  may be marked by an orientation point, such as the set screw  82  or some other indicia, to establish relative rotational displacement between the adjustment ring  84  and the second member  62 . A snap ring  63  cooperates with snap ring groove  65  to limit the travel of locking means  64 . 
     An additional feature of this capper assembly  10  is the plunger member  88  which is circumferentially disposed about the lockout rod  30 . The plunger  88  is biased by spring means  90  which extend between the upper housing  14  along the upper housing member defining the chamber  32  and supported by thrust bearings  92  disposed between the spring and the upper portion  94  of the plunger  88 . The plunger  88  is adapted to provide controlled downward pressure against the top of a bottle cap held in the chuck assembly  22 . The bottom portion  96  of the plunger  88  contacts the face of the cap. However, the plunger  88  is retained so as to be freely rotatable within the lower portion  20  of the clutch housing  16 . This permits the plunger to provide force to the cap while at the same time not scuffing the top of the cap as the chuck assembly tightens the cap onto the bottle. 
     The clutch assembly has a further adjustment feature that permits the zeroing of the magnetic clutch to a predetermined set value after the manufacture and assembly of the head set  10  is completed. This feature allows for the accurate calibration of each individually manufactured head set to a pre-established or desired value. The lower magnetic ring  56  which is mounted in the upper portion  18  of the clutch housing  16  permits this factory or calibrated adjustment of the magnetic clutch. The magnetic ring  56  is retained in the downwardly depending side walls of the upper housing portion  18  of the clutch housing  16  by means of mated threads provided on the magnetic ring  56  and the lower arms  98 . With the adjustment ring  84  indicia  82  at a predetermined position, which indicates what will eventually be, after calibration the “zero” position, the threaded magnetic ring  56  is rotated to adjust the air gap with the magnetic ring  58 . When the desired air gap is achieved, the magnetic ring  56  is locked in this position by a set screw  100 . This final calibration permits the precise alignment of the pair of magnetic rings  56  and  58 . Subsequent adjustment of the magnetic clutch is accomplished through the adjustment ring. 
     Thus it can be seen that the upper housing  14  when driven by the spindle mounting collar  12  causes the rotation of the upper portions  18  of the clutch housing  16 . By means of the magnetic clutch  54  the lower portion  20  of the clutch housing  16  is driven. However, when the torque limit is reached, the lower portion  20  of the clutch housing will cease to rotate notwithstanding the continued rotation of the upper housing  14 . 
     It is intended to cover by the appended claims all modification which come within the true spirit and scope of the invention.