Abstract:
A system for filling pre-charged aerosol cans comprising a frame, a power actuator on the frame having an output member that extends forcibly downwardly through a stroke of fixed length and retracts upwardly, a combined reservoir and filling head supported in the frame generally below the output member, the filling head having a cylindrical dispensing bore and an outlet below the bore adapted to be coupled to the valve of the aerosol can, a dispensing piston with a lower face operable in the bore to create hydraulic pressure on liquid received in the bore from the reservoir, a set of cooperating elements for coupling a dispensing piston to the output member selectively at a plurality of predetermined fixed spacings from the output member, whereby the volume of fluid displaced from the dispensing chamber by the dispensing piston is regulated to fill cans of different capacity while the output member of the power actuator traverses its stroke of constant length.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to apparatus for injecting liquid into pre-charged aerosol cans. 
       PRIOR ART 
       [0002]    My prior U.S. Pat. No. 5,535,790, 5,740,841, and 6,948,534 disclose examples of can filling apparatus of varying complexity and features. The apparatus shown in these patents and the products of others range from simple manually operated devices to semi-automatic power-operated apparatus. There has remained a need for power-operated apparatus that is simple in construction, economical to manufacture, easy and safe to operate, relative fast in operation, and compatible with cans of various sizes and different style valves. 
       SUMMARY OF THE INVENTION 
       [0003]    The invention provides power operated apparatus for filling pre-charged aerosol cans with predetermined quantities of liquids. The apparatus is operated by a pneumatic piston that drives a liquid displacing piston, in tandem with the pneumatic piston, through a swept volume sufficient to fill a can of maximum designated size with a single stroke. The apparatus preferably includes a set of piston rod extensions of different lengths, each length corresponding to a particular size can to be filled. The apparatus also preferably includes a set of pistons of various heights for fine regulation of the amount of liquid to be injected into a pre-charged container so as to adjust, for example, the fill where the density of the liquid material being dispensed into the can varies from product to product and the fill condition is determined by weight. 
         [0004]    The disclosed filling apparatus preferably is both pneumatically controlled and pneumatically power driven making its installation a simple matter of connecting it to an air line and making its operation free of electrical hazards. The pneumatic control system provides a pair of interlocks that assure a can is in place and is not overfilled and that a protective door is closed and latched before and while pump injecting action occurs. 
         [0005]    The filling system afforded by the invention meets the need for a device with the capacity to quickly and efficiently fill cans of different sizes, cans of different valve styles, and with the ability to adjust the fill quantity. This is accomplished with the invention using automatic controls that afford the safety features referenced above and that are simple and reliable. 
         [0006]    Central to the simplicity of the filling system of the invention is an arrangement and operation strategy where a single stroke of a dispensing piston is sufficient to fill the largest can size for which the system is designed. When cans of a lesser volume are being filled, the apparatus is fitted with a dispensing piston rod extension having a correspondingly shorter length. A set of pistons of various heights, each compatible with any piston rod extension, additionally enables the dispensing volume to be closely adjusted to account for density variations. 
         [0007]    Cans with a particular style of valve with a male tip are difficult to fill with practical speeds when dispensing piston pressure is necessarily limited. This difficulty is the result of an obstruction to inlet flow to the can presented by a check ball used in the filling device to prevent escape of liquid from a supply reservoir when not coupled to a can valve. In accordance with the invention, a deflector element is interposed in the path the check ball takes when the ball is lifted from a seat in the filling head by the insertion of the valve tip of the can to be filled. The deflector, while allowing the check valve ball to fully seal on the seat is operable to displace the ball laterally off the top of the can valve member when the latter moves the ball off its seat. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a somewhat schematic perspective view of the housing and general arrangement of the can filling system of the invention; 
           [0009]      FIG. 2  is a somewhat diagrammatic, fragmentary cross-sectional view of a filling head area of the can filling system; 
           [0010]      FIG. 3  is a diagrammatic showing of the can filling system illustrating the methodology of accommodating different size cans using a set of piston rod extensions of different lengths; 
           [0011]      FIG. 4  is an illustration of a set of various height pistons used to provide fine adjustment of the injected liquid volume for the can filling system of the invention; 
           [0012]      FIG. 5  is an enlarged cross-sectional view of the filling head of the invention for use with male tip valve style cans; 
           [0013]      FIG. 6  is a view similar to  FIG. 5  but without a male tip valve inserted; and 
           [0014]      FIG. 7  is a schematic diagram of a pneumatic control circuit for the can filling system of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    A filling system of the invention in the illustrated embodiment has a housing frame  10  that encloses a reservoir and can receiving area  11  and a pneumatic control and actuator compartment  12  overlying the receiving area. The housing frame  10  is fabricated primarily of sheet metal forming a rectangular cabinet. A door  13  opens and closes for access to the reservoir and can receiving area  11 . The door  13 , formed of a heavy sheet of polycarbonate or other preferably transparent suitable material is carried by a piano-type hinge  14  along one vertical edge. 
         [0016]    At a mid-section of the receiving area  11 , is a horizontal support plate  16  rigidly attached to the sides of the housing  10 . The support plate  16  has a laterally centered slot  17  open at an edge facing the door  13 . Either of two different filling heads  18 , described first, and  118 , described below, are received in the slot  17 . The filling head  18  has a central cylindrical bore  19  forming a pumping chamber from which liquid, for example, paint, is forced into a pre-charged aerosol can  21 . The filling head  18  is removably coupled in a liquid tight manner by threading it into a boss on the bottom of a liquid reservoir  22 . The reservoir  22  can be an open top rectangular pan optionally fitted with a cover. The filling head  18  and reservoir  22  can be fabricated of aluminum, for example. The filling head  18  has a peripheral groove  20  that interfits with the slot  17  enabling the head, carrying the reservoir  22  to be slid onto the support plate  16 . 
         [0017]    U.S. Pat. No. 6,948,534, the disclosure of which is incorporated herein by reference, explains details of a dispensing valve  23  at the lower end of the filling head  18 . Briefly, when a ball  24  is forced off its seat, liquid in the reservoir  22  is dispensed through a hollow injector pin  26  into a female valve  27  of a can  21 . 
         [0018]    A pneumatic actuator  31  in the form of a piston  32  and cylinder  33  (schematically shown in  FIG. 3 ) is contained in the compartment  12 . The piston  32  is relatively large, being, for example, 5 inches in diameter. A piston rod  34 , representing the output of the actuator  31 , has its free end extending into the reservoir and can receiving area  11  and is internally threaded for receiving a short externally threaded stud  36  of a piston rod extension  37 . The piston rod extension at a lower end  38  has an axial threaded bore  39  and a counter bore  41  to receive the end of a machine screw  42  and a nut  43 , respectively. The machine screw  42  serves to retain a dispensing piston  44  on the piston rod extension  37 . 
         [0019]    The dispensing piston  44 , which preferably is formed of a thermoplastic material such as Delrin® or other suitable material, has an integral peripheral sealing skirt  47  formed by the presence of a deep groove  48  in its lower pressure developing face  49 . The body of the piston  44  has a reduced outside diameter rearward of the sealing skirt  47 . The groove  48  allows for limited radial movement of the sealing skirt  47  or ring to properly fit the filling head bore  19  and increase its sealing capacity with this bore in proportion to the pressure being developed by the piston  44 . 
         [0020]    When the pneumatic piston  33  ( FIGS. 3 and 7 ), is driven downwardly by air pressure introduced into a chamber  56  above the piston, the dispensing piston  44 , carried by the piston rod extension  37 , is driven into the filling head bore  19  so as to express liquid in this bore past the ball valve  23  through the injector pin or stem  27  into the can  21 . The reservoir  22  preferably has the capacity to store enough liquid to fill a plurality of cans. For example, the reservoir can contain enough liquid to fill twenty six (26) 16 ounce cans and proportionately more cans when the latter are of smaller size. 
         [0021]    A can  21  is manually loaded in the area  11  of the housing on a platform  61 . The platform  61  is raised by manually operating a lever  62  that turns a cam  59  to move the platform upwardly through force developed in a spring  60  ( FIG. 3 ). Reference can be made to U.S. Pat. No. 5,535,790 for details of a mechanism for raising the platform. As the can  21  is raised by the platform  61 , the fill head injector pin or stem  26  pushes into the valve of the can  21 . 
         [0022]    As suggested in  FIG. 3 , when the pneumatic piston  33  is fully retracted, the dispensing piston  44  is out of the filling head pumping chamber  19  thereby allowing liquid in the reservoir  22  to fill into this chamber. When the pneumatic piston  33  has pressurized air introduced into the chamber  56  above it, it descends and forces the dispensing piston  44  into the filling head chamber  19  such that the ball valve  23  is opened and liquid flows from the pumping chamber  19  into the can  21 . 
         [0023]    A pneumatic control circuit  66  of the can filling apparatus is illustrated in  FIG. 7 . The circuit  66  senses certain conditions in the apparatus and power operates the dispensing piston  44 . The circuit  66  may include an air filter  67  and pressure regulator  68 . A supply line  69  feeds air under pressure to the filter  67 . The circuit  66  includes a limit poppet valve  71  disposed in the bottom of the housing  10  and a limit poppet valve  72  as well as a spool directional control valve  73  in the upper compartment  12 . More specifically, the limit valves  71 ,  72  are mechanically operated 2-position, spring offset 3-way poppet valves. The valve  73  is a 5 ported double air piloted spring offset 4-way direction control valve. The valving elements of these respective valves  71 - 73  are biased to certain conditions by springs  76 - 78 . 
         [0024]    The limit valve  71  is responsive to the vertical position of the can support platform  61  while the limit valve  72  is responsive to the angular position of a latch knob  81  on the door  13 . A vertical rod  84  ( FIG. 1 ) within the housing  10  converts the pivotal latched and unlatched positions of the knob  81 , respectively, to high or low positions of the rod which, in turn, are sensed by the limit valve  72 . The latch knob  81  serves to hold the door  13  closed when it is in a latching position and unless the door  13  is closed, the vertical rod  84  cannot signal that the door is latched closed. The circuit  66 , as will be explained, will cause the piston  33  of the pneumatic actuator  31  to force the dispensing piston  44  into the filling head bore  19  when the platform  61  is raised by operation of the lever  62  and the door  13  is latched by the knob  81 . If either of these conditions, namely an elevated platform  61  or a latched knob  81  does not exist, the circuit  66  will maintain the pneumatic piston  33  in its upward retracted position or will initiate movement to this position. 
         [0025]    In greater detail, when the can platform  61  is raised, the spring  76  shifts the poppet of its valve  71  leftward from the position shown in  FIG. 7  such that it exhausts air pressure from a line  82  which removes any pressure bias towards the left on a spool  83  of the directional control valve  73 . When the latch knob  81  is in a latching position to hold the door  13  closed, the poppet of the associated limit valve  72  is forced out of the position illustrated in  FIG. 7  against the bias of the spring  77  to connect a pressurized line  86  to a pilot line  87 . Pressure in the pilot line  87  drives the spool  83  to the right as viewed in  FIG. 7  overcoming the bias of the spring  78 . In the rightward position of the spool  83 , a pressure line  89  supplies pneumatic pressure through the spool to a line  91  causing the pneumatic piston  33  to be forced downwardly by pressurizing the chamber  56  above it. Simultaneously, a chamber  90  below the piston  33  is exhausted through a line  92  in this rightward position of the spool  83 . If the latch knob limit valve  72  supplies pilot pressure through the line  87 , this pressure is ineffective to shift the spool  83  to extend the piston rod  34  where the platform  61  is lowered and the pilot line  82  fed by the limit valve  71  supplies pressure to the right side of the spool  83 . 
         [0026]    Whenever the latch knob is in an open position, the valve  72  reverts to the position illustrated in  FIG. 7  and exhausts the pilot line  87  with the result that the spring  86  of the directional control valve  83  assumes the position indicated in  FIG. 7  and the piston  33  is forced to retract by pressure delivered to the chamber  90  under the piston by the line  92 . Regardless of the position of the latch knob and the valve  72  a lowering of the can platform  61  will cause the pilot line  82  to be pressurized and, with the assistance of the spring  86  will cause the spool of the directional control valve  73  to shift to the left taking the position illustrated in  FIG. 7 . Again, this latter situation will cause the piston  33  to retract. A benefit of the disclosed circuit  66  is that if a can is inadvertently subjected to over-filling such as would occur where there was an inadvertent attempt to fill it twice, the platform  61  will be depressed against the spring  60  by vertical expansion of the can and the limit valve  71  will be actuated to pressurize the pilot line  82  and, consequently, retract the piston  33 . The operator of the apparatus can abort the fill sequence at any time by rotating the latch knob  81  to its unlatched position causing the piston  33  to retract. From the foregoing, it will be seen that the pneumatic control circuit  66  is exceptionally simple making it economical to construct, reliable in operation, and easy to trouble shoot if needed. 
         [0027]    Currently, in the United States of America, for example, there are three popular aerosol can sizes, namely,  16 ,  12  and  6  ounce sizes. The apparatus of the invention includes a set of piston rod extensions  37   a ,  37   b , and  37   c  ( FIG. 3 ) of different lengths, each corresponding to an individual can size that is intended to be filled by the apparatus. Preferably, the dispensing chamber  19  is sized to hold a volume at least equal to the volume of the largest size can to be filled with the apparatus. The longest of the piston rod extensions  37   a  is used for filling the largest can size. 
         [0028]    Smaller can sizes are filled using proportionately shorter length piston rod extensions, e.g.  37   b ,  37   c . This methodology works because under normal conditions, the pneumatic piston  33  operates through a stroke of constant length which measured along the dispensing chamber  19  equates to a swept volume at least equal to the capacity of the largest can to be filled by the apparatus. When the volume of liquid to be dispensed into a can is less than the capacity of the dispensing chamber  19 , a short piston rod extension  37   b , or  37   c  is mounted on the piston rod  34 . The upper end of each piston rod extension  37  has a threaded stud  36  that screws coaxially into a mating threaded blind hole  97  in the lower end of the piston rod  34 . The portion of the stroke of the pneumatic piston  33  before the dispensing piston  44  enters the chamber  19  is ineffective to dispense liquid from the chamber because no hydraulic pressure can be developed by the dispensing piston during this movement when it is out of the chamber. The shorter the piston rod extension  37   b , or  37   c , the less liquid will be dispensed out of the chamber  19 . 
         [0029]    Government regulations specify that the contents of an aerosol can containing a liquid be specified by weight. The density of different liquids, or the same liquid with different additives including pigments, can vary considerably. This difference in density, when the contents are specified by weight, has a corresponding influence on the volume of a liquid. Economics dictates that a can should not be overfilled when, for example, a liquid is of relatively high density. The invention solves the problem of over filling by enabling the user to make minor adjustments to the volume of liquid dispensed into a can of a nominal regular size. This volume adjustment in accordance with the invention involves making minor axial adjustments to the position of the lower pressure developing face of the dispensing piston  44 , relative to the pneumatic piston  33 , that are small compared, for example, to the differences in the lengths of the piston rod extensions  37   a, b , and  c,  that, as explained, account for different commercial regular can sizes. A preferred manner of accomplishing this minor adjustment is illustrated diagrammatically in  FIG. 4  where a set of pistons  44   a - d  of varying height are provided. If a user wants to increase the dispensed volume, he selects a thicker or taller piston and, vise versa, if he wants to decrease the dispensed volume he selects a thinner or shorter piston. By way of example, the pistons can vary in thickness, i.e. height, by ⅛ inch. The same set of dispensing pistons  44   a - d  can be used with any of the illustrated piston rod extensions  37   a - c . The same effect can be achieved by using a single thin piston with shims of different thickness and/or the same thickness but different numbers of shims. Alternatively, the shims can be interposed between the extension  37  and the pneumatic piston rod  34 . Still further, it is contemplated that a screw adjustment of the piston or extension to slightly vary the position of the lower face of the dispensing piston  44  relative to the pneumatic piston rod  34  is contemplated. All of the foregoing techniques of varying the position of the lower face of the dispensing piston relative to the pneumatic piston rod  34  can, in accordance with the invention, effect a desired minor adjustment in the dispensing or fill volume of liquid being dispensed by the apparatus. 
         [0030]    Referring to  FIGS. 5 and 6 , there is shown a filling head  118  for use with a male tip style can valve  102 . The filling head  118  can be substituted in the housing  10  for the head  18 . The head  118  has a cylindrical dispensing chamber  103  corresponding to the chamber  19 . Below the dispensing chamber  103  is a dispensing port  104  in the form of a stepped bore  104  through a bottom end wall  106  of the filling head. At an upper end of the bore or dispensing port  104  is a circular edge  107  that forms a valve seat for a valve ball  108  made of steel or other suitable material. A horizontal pin  109 , such as a dowel pin, in the chamber  103  overlies the valve seat  107 . The bore  104  is configured to couple in a liquid tight manner with a male valve tip or stem  105  of a can to be filled. Additionally, the bore  104  and surrounding parts of the end wall  106  are configured to cause the end of the male tip valve stem  105  to displace the ball  108  from the seat  107  when the stem projects through the plane of the seat  107 . The dowel pin  109 , preferably of non-magnetic stainless steel, fixed by a press fit in a hole  110  radial to the axis of the filling head chamber  103  extends from the side of the body of the filling head  118  radially to a zone generally above the seat  107 . An end  111  of the pin  109  is situated in a path taken by the ball  108  when it is raised off of the seat  107  by the end of the stem  102  such that it constrains the ball  108  to a path preventing it from seating symmetrically on the upper end of the stem. The male tip or stem  102  is a hollow cylindrical tube typically molded of plastic. This deflection of the ball  108  from a vertical path that it would otherwise take as it is raised off the seat  107  by the stem tips the ball on the edge of the stem and thereby prevents the ball from seating on this edge. As a result, the liquid in the bore or chamber  103  can be dispensed into a can at a practical fill rate with moderate pressure developed on the liquid in the bore so that the pneumatic actuator can operate at normal shop pressure of, for example, about a 85 to about 110 psig. 
         [0031]    While the invention has been shown and described with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein shown and described will be apparent to those skilled in the art all within the intended spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.