Abstract:
A closer for pressing a lid onto a container includes a presser foot mounted for reciprocating movement into and out of force applying engagement with the lid; an actuator moveable between retracted and extended positions; and a force multiplying assembly disposed in operative relationship intermediate the presser foot and the actuator for multiplying an input force from the actuator to a predetermined maximum lid pressing force at the extended position.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to closing and sealing of fluid containers. 
     Various kinds of fluids are stored in containers that must be tightly sealed. For example, paint is often sold in plastic or metal cans with press-fit lids. 
     Paint is often tinted by mixing appropriate amounts of colorants into a can of base paint. The paint can is capped with a press-fit lid and agitated, which thoroughly mixes the colorant throughout the base paint and produces paint of the desired color. The machines used to mix the paint subject the can to high forces, and require that the can be securely sealed and undamaged in order to avoid leakage or failure. 
     The most common method for sealing a paint can involves hammering the lid down with a rubber mallet or similar tool. This is inconsistent and can cause paint spillage. The prior art has attempted to replace the mallet with hand-operated press-type sealing machines or “closers” that multiply manual force to the required level. However, these machines are dependent on operator skill to achieve consistent sealing, and are also capable of crushing a paint can if used too vigorously. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a container closer that provides a consistently high closing force independent of operator technique. 
     It is another object of the invention to provide a container closer that limits the force applied to a can lid. 
     It is another object of the invention to provide a container closer which is relatively insensitive to the alignment of the container. 
     These and other objects are met by the present invention, which according to one embodiment provides a container closer for pressing a lid onto a container, including a presser foot mounted for reciprocating movement into and out of force applying engagement with the lid; an actuator moveable between retracted and extended positions; and a force multiplying assembly disposed in operative relationship intermediate the presser foot and the actuator for multiplying an input force from the actuator to a predetermined maximum lid pressing force at the extended position. 
     According to another embodiment of the invention, an elastic member forms a part of the interconnection between the actuator and the presser foot, and is arranged such that the lid pressing force is proportional to the displacement of the actuator; and the actuator has a limited throw such that the elastic member maintains a margin of elastic deflection at the extended position of the actuator. 
     According to another embodiment of the invention, the elastic member is a coil spring. 
     According to another embodiment of the invention, the container closer further includes a reciprocating shaft connected to the presser foot and adapted to be driven by the actuator; and an elastic member interconnecting the shaft and the force multiplying assembly such that the lid pressing force is proportional to the displacement of the elastic member. 
     According to another embodiment of the invention, a distance representing the overall length of the presser foot and the shaft is adjustable. 
     According to another embodiment of the invention, the force multiplying assembly includes a stationary mounting block; a lever arm pivotally connected to the mounting block, the lever arm having a first end connected to the actuator and a second end carrying a cam; and a cam follower disposed between the cam and the elastic member. 
     According to another embodiment of the invention, the closer further includes a top plate disposed at an upper end of the shaft; and a retraction roller carried by the second end of the lever arm and positioned to contact the top plate on upward motion of the second end of lever arm. 
     According to another embodiment of the invention, the closer includes a pushrod connecting the actuator and the first end of the lever arm. 
     According to another embodiment of the invention, the actuator is a manually-operable handle. 
     According to another embodiment of the invention, the closer further includes a housing having: a base plate; a pair of spaced-apart side walls extending upwards from the base plate; and a top plate extending between upper ends of the side walls, the top plate carrying the presser foot, actuator and force multiplying assembly. The housing is adapted to receive a container underneath the presser foot. 
     According to another embodiment of the invention, a container support is disposed between the side walls and moveable between: a first position in which the container support is clear of the presser foot to allow a can of a first size on the base plate under the presser foot; and a second position in which the container support is disposed under the presser foot so as to support a can of a second size under the presser foot. 
     According to another embodiment of the invention, the container support is mounted for pivoting movement between the first and second positions. 
     According to another embodiment of the invention, at least one alignment stop is disposed on the container support so as to align a can in a centered position underneath the presser foot. 
     According to another embodiment of the invention, at least one alignment stop is disposed on the base plate so as to align a can in a centered position underneath the presser foot. 
     According to another embodiment of the invention, the presser foot is sized to engage the lid while maintaining a clearance between the presser foot and a can rim surrounding the lid. 
     According to another embodiment of the invention, the presser foot has a convex curved working face. 
     According to another embodiment of the invention, the presser foot has a stepped working face with an outer portion sized to contact the lid of a first size container, and an inner, downward-protruding portion sized to contact the lid of a second size container smaller than the first size container. 
     According to another embodiment of the invention, the presser foot includes an outer ring sized to contact the lid of a first size container, and a coplanar inner ring sized to contact the lid of a second size container smaller than the first size container. 
     According to another embodiment of the invention, the actuator is a powered actuator, and means are provided for limiting the displacement imparted to the force-multiplying assembly by the actuator. 
     According to another embodiment of the invention, the closer further includes means for preventing operation of the actuator in response to the presence of any portion of a person&#39;s body underneath the presser foot. 
     According to another embodiment of the invention, the closer further includes means for operating the actuator in response to the presence of a container underneath the presser foot. 
     According to another embodiment of the invention, in a closer of the type for sealing a cylindrical can which has a raised peripheral can rim disposed at its upper end, and a press-fit lid having a flat center section and an upwardly-extending lid rim, the lid rim sitting below a plane of the can rim in a fully sealed condition, wherein the closer includes an actuator which moves a presser foot into and out of force applying engagement with the lid, the improvement includes: the presser foot having a working face which is sized to engage the lid rim while maintaining a clearance between the presser foot and the can rim. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter that is regarded as the invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
         FIG. 1  is a perspective view of a container closer constructed according to the present invention; 
         FIG. 2  is a front view of the closer of  FIG. 1 , with a container support thereof in a raised position; 
         FIG. 3  is another front view of the closer of  FIG. 1 , with a container support thereof in a lowered position; 
         FIG. 4  is a front perspective view of a portion of the closer of  FIG. 1 , with a cover removed to show the internal mechanism thereof; 
         FIG. 5  is a rear perspective view of the mechanism shown in  FIG. 4 ; 
         FIG. 6  is a top view of the base plate of the closer of  FIG. 1 ; 
         FIG. 7  is a top view of a container support in a lowered position; 
         FIG. 8  is a side cross-sectional view of the closer of  FIG. 1 , with an operating handle in a raised position; 
         FIG. 9  is a side cross-sectional view of the closer of  FIG. 1 , with an operating handle in a lowered position; 
         FIG. 10  is a front view of a portion of the closer shown in  FIG. 1 , with its cover removed, with a presser foot in a raised position above a container; 
         FIG. 11  is another view of the closer shown in  FIG. 10 , with a presser foot forcing a lid onto the container; 
         FIG. 12  is another view of the closer shown in  FIG. 10 , with a presser foot retracted after having pressed a lid onto a container; 
         FIG. 13A  is a perspective view of an alternative presser foot; 
         FIG. 13B  is a cross-sectional view of the presser foot of  FIG. 13A ; 
         FIG. 14A  is a perspective view of another alternative presser foot; 
         FIG. 14B  is a cross-sectional view of the presser foot of  FIG. 14A   
         FIG. 15  is a side view of a presser assembly including an adjustment mechanism; and 
         FIG. 16  is a side view of an alternative presser assembly including a powered actuator. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,  FIG. 1  shows an exemplary container closer, simply referred to as a “closer”, and denoted  10 . The closer  10  is especially adapted to press lids onto standardized paint cans, but it may be used with any type of container having a press-fit lid. The closer  10  includes a base plate  12  and a housing  14  with spaced-apart side walls  16  and  18  and a top wall  20 . The housing  14  carries a presser assembly  22  (see  FIG. 2 ) which is moved up and down by a force multiplying assembly  24  that is enclosed by a cover  26 . An actuator  28  is provided to operate the closer  10  and is moveable between retracted and extended positions. In this example the actuator  28  is a handle having a pair of curved, spaced-apart arms  30 A and  30 B, and hand grips  32 A and  32 B. 
     The housing  14  is adapted to receive and hold a paint can and align it under the presser assembly  22 . A flat container support  34  is carried inside the housing  14 , and is mounted by way of hinge pins  36  at its aft end, and bearing pins  38  at its forward end, which ride in arcuate slots  40  formed in the side walls  16  and  18  of the housing  14 . When the container support  34  is in the raised position, shown in  FIG. 2 , a relatively large can such as a standard one-gallon paint can may be placed under the presser assembly  22 . When the container support  34  is in a lowered position, shown in  FIGS. 1 and 3 , a smaller container such as a standard one-quart paint can may be placed under the presser assembly  22 . 
     The container support  34  includes a pair of protruding alignment stops  42  (see  FIG. 7 ) that are positioned to align a standard one-quart can “Q” in a centered position below the presser assembly  22 . The base plate  12  includes a second pair of protruding alignment stops  44  that are positioned to align a standard one-gallon can “C” in a center position below the presser assembly  22  (see  FIG. 6 ). 
     Referring to  FIGS. 2 and 3 , the presser assembly  22  includes a presser foot  46  connected to the lower end of a main shaft  48 . The main shaft  48  has a lower portion  50  which defines a shoulder  52  and an upper, reduced-diameter portion  54 . A top plate  56  is disposed at the upper end of the main shaft  48 . A cam follower  58  is mounted for sliding movement on the upper portion  54  of the main shaft  48 , and an elastic member  60  is disposed between the shoulder  52  and the cam follower  58 . The entire presser assembly  22  is mounted within a sleeve  62  and is moveable between a raised position and a lowered position, relative to the housing  14 . 
     The elastic member  60  may be any structure which is capable of interconnecting the presser foot  46  and the actuator  28  (the connection may be direct or indirect) and which exhibits recoverable elastic deflection when compressed, with a predictable force-displacement relationship. In the illustrated example, the elastic member  60  is a metallic, compression-type coil spring. The elastic member  60  may be placed in any location within the mechanical interconnection between the actuator  28  and the presser foot  46 . 
       FIGS. 4 and 5  illustrate the force multiplying assembly  24  in more detail. A stationary mounting block  64  is mounted to the top wall  20  of the housing  14 . It is noted that the moveable components of the force multiplying assembly  24  are arranged in symmetrical pairs on opposite sides of the mounting block  64 . However, for purposes of clarity in explanation, only one set of moveable components will be described. 
     A generally horizontal lever arm  66  with forward and aft ends  68  and  70  is connected to the mounting block  64  at a lever pivot  72  which is disposed closer to its forward end  68 . A cam block  74  disposed at the forward end  68  of the lever arm  66  carries a rotatable, generally cylindrical cam  76 , and a retraction roller  78  positioned above the cam  76 . The cam  76  is positioned by the lever arm  66  so that its axis of rotation is generally aligned with the vertical axis of the main shaft  48 . Accordingly, downward motion of the forward end  68  of the lever arm  66  causes the cam  76  to bear against the cam follower  58 , and upwards motion of the lever arm  66  causes the retraction roller  78  to bear against the top plate  56 . 
     The inner end of the actuator arm  30  is connected to the mounting block  64  by an actuator pivot  80 . The actuator arm  30  includes a short arm  82  which protrudes aft from the actuator pivot  80 . A generally upright pushrod  84  interconnects the short arm  82  and the aft end  70  of the lever arm  66 . A return spring  86  interconnects the lever arm  66  and the mounting block  64 , and biases the lever arm  66  towards the retracted position. 
     The actuator  28 , pushrods  84 , and lever arm  66  are arranged to provide multiplication of an input force applied by the actuator  28  to a desired output force on the presser assembly  22 . In this example, there is a two-stage compound leverage, with a total force multiplication ratio of about 20:1 (and an inverse displacement ratio). However, the location of pivot points, etc., the number of stages of multiplication, or the type of force-multiplying assembly could be modified as required to suit a particular application. 
     Referring now to  FIGS. 10-12 , a typical can “C” and lid “L”, and the presser foot  46 , are shown in more detail. While paint cans vary in size, shape, and construction, the can C shown in partial cross-section in  FIG. 10  is generally representative of the most common type of paint can. The can C is cylindrical, with a peripheral can rim  88  at its upper end  90 . A flange  92  is disposed at the can&#39;s upper end  90  and forms a concave peripheral groove  94 . The lid L has a flat center section  96 , an upwardly-extending lid rim  98 , and a downwardly-extending peripheral bead  100 . The bead  100  is sized and shaped to securely engage the groove  94  when the lid L is fully seated, forming a liquid-tight seal. 
     It should be noted that, in the fully seated position (see  FIG. 12 ), the lid rim  98  sits below the plane of the can rim  88 . Therefore, in order to fully seat the lid L, it is preferred that the presser foot  46  not contact the can rim  88  during the closing process. At the same time, it is desirable to use a single presser foot  46  for various sizes of cans. A substantial load, for example at least about 100 Kg (220 lbs.) is required to fully seat the lid L, but the maximum load and the displacement must also be limited to avoid crushing of the can C. It is desirable to apply the closing force to the lid L through the lid rim  98  and not the thin center section  96 . 
     As shown in  FIG. 10 , the presser foot  46  has a convex-downward working face  102 , with an approximately spherical curvature. The radius of curvature is chosen such that the working face  102  will contact the lid rim  98  of various sizes of cans but will not contact the can rim  88 . The curved shape helps ensure contact with the lid rim  98  even if the can C is not perfectly centered under the presser foot  46 . 
       FIGS. 13A and 13B  illustrate an alternative presser foot  146 . Its working face  148  is stepped and has an outer portion  150  and a downward-protruding inner portion  152 . The outer portion  150  is sized to contact the lid rim  98  of a one-gallon can C, while the inner portion  152  is sized to contact the lid rim of a one-quart can (not shown). A notch  154  is formed around the outer periphery of the outer portion  150  so as to avoid contact with the can rim  88 . 
       FIGS. 14A and 14B  illustrates another alternative presser foot  246 . Its working face  248  defines an outer ring  250  and a coplanar inner ring  252 . The outer ring  250  is sized to contact the lid rim  98  of a one-gallon can C, while the inner ring  252  is sized to contact the lid rim of a one-quart can (not shown). The outer diameter of the outer ring  250  is limited so as to avoid contact with the can rim  88 . 
     The operation of the closer  10  will now be explained in detail with reference to  FIGS. 10-12 . First, the container support  34  is placed in the correct raised or lowered position for the size of can C to be closed. A can C is then placed either on the container support  34  or the base plate  12  against the alignment stops  42  or  44 , as shown in  FIGS. 7 and 6 , respectively. This ensures the can C is centered under the presser foot  46 . The lid “L” is placed on the can C with the bead  100  aligned with the groove  94  (this may be done before or after inserting the can C in the closer  10 ). The actuator  28  is then pulled downward, forcing the pushrod  84  up and pivoting the forward end of the lever arm  66  and the attached cam  76  downward. The cam  76  contacts the cam follower  58  and displaces the main shaft  48  and attached presser foot  46  downwards until the attached presser foot  46  contacts the lid L. Further downward motion of the cam  76  causes the elastic member  60  to compress as the bead  100  of the lid L is forced into the groove  94  of the can C. 
     The actuator  28  is stopped at the end of its throw by contact with the front edge of the housing  14 , as best seen in  FIG. 9 . A bumper  104  may be provided on the housing  14  to prevent noise and damage. The fully sealed lid L is shown in  FIG. 11 . Once the seal is completed, the actuator  28  is released and returns to its upper position under the bias of the return springs  86  (see  FIGS. 8 and 12 ), retracting the lever arm  66  with it. As it moves upward, the forward end of the lever arm  66  moves upward, causing the retraction roller  78  to bear against the top plate  56  and pull the entire presser assembly  22  clear of the can C. The can C may then be removed. 
     The effective spring rate of the elastic member  60  is chosen in conjunction with the throw (i.e. input displacement) of the actuator  28  and the dimensions of the housing  14 , considering the height of the can C, so that a margin of elastic deflection is always maintained. In other words, in normal operation the closer  10  never experiences a “solid” mechanical interconnection between the actuator  28  and the presser foot  46  in the “closing” direction. Therefore, during the closing operation described above, the maximum force applied to the lid L and can C is independent of the input force. For example, if an input force in excess of the minimum required is applied, it will simply cause the entire mechanism to accelerate until the actuator  28  contacts the housing  14 . The result is a lid-closing cycle with consistently high but not excessive force, with no specific operator technique required. In contrast, prior art closers which simply multiply an input force can be used to apply excessive force to the can C. 
     As an illustrative example, the elastic member  60  may be assumed to have an effective spring rate “K” over its operating range (typically expressed in Kg/cm or lbs./in.) The actual spring rate K will be chosen to accommodate the specific application, depending on the force requirements of the container to be closed. A movement of the actuator  28  through an effective throw designated “T”, that is, a displacement after the elastic member begins to compress, with an effective leverage ratio of “R”, will compress the elastic member  60  a distance equal to T/R. This will result in a maximum force on the can C equal to K*(T/R). The amount of this force that the lid L actually “sees” is dependent on the flexibility of the can C. Because of the compound leverage ratio R, the input force required to complete this motion is well within the physical ability of most all potential operators of the closer  10 . 
     The maximum force applied to the can C will vary depending on the height of the can C, which may vary from manufacturer to manufacturer or among different production runs. To accommodate this variation, the closer  10  may incorporate means for adjusting the maximum force applied to the can C. For example,  FIG. 15  illustrates an alternative presser assembly  22 ′ similar in construction to the presser assembly  22  described above and having a main shaft  48 , cam follower  58 ′, top plate  56 ′, elastic member  60 ′, and presser foot  46 ′. A threaded adjustment shaft  106  protrudes downward from the main shaft  48 ′. The presser foot  106  has a stub shaft  108  with complementary female threads. This allows the total distance “D” from the neutral position of the cam follower  58 ′ to the presser foot  46 ′ to be varied. If a relatively taller can C is used with a fixed throw endpoint of the actuator  28 , this will result in more compression of the elastic member  60  and higher maximum force on the can C, so the distance “D” would be shortened to compensate. With the same actuator throw endpoint, a relatively shorter can C would result in less compression of the elastic member  60  and lower force, so the distance “D” would be increased to compensate. The adjustment may be locked with a jam nut  110  or other suitable locking mechanism. 
     The invention has been described above with respect to manual operation. However the closer  10  may also be adapted powered operation. For example,  FIG. 16  illustrates an alternative presser assembly  122  having a main shaft  148 , cam follower  158 , top plate  156 , elastic member  160 , and presser foot  162 . The cam follower  158  includes a vertical rack gear  164 . An electric motor  166  carries a pinion gear  168  which is engaged with the rack gear  164  to drive the cam follower  158  up or down as required. 
     A suitable power supply and controls are provided for the electric motor  166 . These are shown schematically in  FIG. 16  and include a power supply  170 , a reversing switch  172 , upper and lower limit switches  174  and  176 , and optionally light beam sensors  178 . The lower limit switch  176  or other suitable displacement sensor is configured to limit the compression of the elastic member  60  substantially as described above for the manually-operated closer  10 . The cycling of the motor  166  may be controlled by the switch  172 , in which case the light beam sensors  178  serve as a safety cut-off device should the operator place his hands or other body parts beneath the presser foot  162  during operation. Alternatively, the controls may be arranged to automatically start the closing cycle when a can C is placed under the presser foot  162 . 
     As an alternative control, there could be two pushbuttons or switches (not shown) installed on top of the closer  10 . In order for the motor to start the user would have to depress both buttons or switches simultaneously. This ensures that the user&#39;s hands are not in contact with the can during operation of the closer  10 . 
     The foregoing has described a closer and method for its operation. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation.