Abstract:
Filling apparatus for female valve type precharged aerosol cans includes an improved check valve construction that effectively reduces leakage and blow back while being both simple and economical. The valve comprises a seat formed of PTFE in the configuration of an O-ring. A can carrier assembly below the filling head supports the can in coupled relation with the filling head. The can carrier utilizes a relatively short compression spring to lift the can into its coupled relationship with the filling head and to laterally stabilize the lower end of the can without auxiliary guides and the like such that the carrier avoids the need for extraneous manipulation of elements other than the can itself when the can is being loaded or unloaded into the apparatus and the carrier cannot be jammed by spilled material.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to improvements in apparatus for filling aerosol cans. 
   PRIOR ART 
   Various devices have been created to inject paint or other material into aerosol cans precharged with solvent and propellant on a custom or other low volume basis. Examples of prior art devices are disclosed, for example, in U.S. Pat. Nos. 5,535,790; 5,647,408; 5,740,841; 5,832,965; and D361,581. Some devices have exhibited a tendency to allow propellant to leak back from a can and, in some cases, are susceptible to “blow back”. In the latter case, where significant leakage flow occurs in an injector circuit, paint or other material in a reservoir on the filling device is uncontrollably expelled by propellant in the aerosol can. This phenomena is the result of large pigment particles or dry paint particles fouling a valve seat or valve ball in the injector circuit and thereby preventing a leak proof seal being established between these valve members. 
   Relative axial movement is ordinarily necessary to couple an aerosol can filling/dispensing opening or port to the filling device. In prior art devices, the injector, along with a superjacent reservoir, is fixed above a can receiving zone. The can is supported in the receiving zone from below on a platform that is vertically moveable toward and away from the injector. Various actuating/guiding mechanisms have been used to elevate and lower the can supporting platform and move the can axially into or out of coupling relation with the injector. These prior art can supporting/transporting mechanisms typically comprise numerous elements that add cost to the manufacture of the can filling device. Additionally, prior art can supporting and transporting mechanisms can be subject to fouling and malfunction when an accidental spill of paint or other material occurs. The parts associated with the mechanism may be difficult to reach and/or disassemble for purposes of cleaning up an accidental spill. 
   SUMMARY OF THE INVENTION 
   The invention provides an aerosol can filling device that is economical to produce, easy to use, and reliable in operation. The device includes an improved filling head with a valve seat construction that avoids critical surface machining in the injector valve seat area while affording a leak and blow back resistant valve operation. This improved valve operation is obtained through the use of a simple O-ring confined in an associated annular pocket. The O-ring forms the seat for a spring biased valve ball. The relatively soft nature of the O-ring, its surface geometry, and material characteristics, for yet unexplained reasons, effectively reduces the occurrence of leaks and blow back from a precharged aerosol can. 
   The filling device includes a simplified can support that enables the operator to load or unload a can to or from a coupled relationship with the filling head by simple gripping and manipulation of the can without requiring extraneous movements of levers or other operating elements. In the disclosed embodiment, the can support is mounted directly on a large diameter, heavy wire spring which is the exclusive locating element for the can support. The spring serves to guide and laterally stabilize the can support without reliance on bearing surfaces, linkages, levers, or the like. As a beneficial consequence, accidental spills of paint or other materials being dispensed into aerosol cans cannot interfere with the function of the support and can be cleaned up without disassembly and/or up-ending the device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an aerosol can filling device embodying the invention; 
       FIG. 2  is a front elevational view of the device; 
       FIG. 3  is a cross-sectional view of a filling head of the device taken in a vertical mid-plane; and 
       FIG. 4  is a cross-sectional view of a can support platform taken in a vertical mid-plane coincident with the plane of  FIG. 3 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings and particularly to  FIGS. 1 and 2 , there is shown an aerosol can filling device  10  for injecting paint or other liquid material into an aerosol can  11  that is prefilled typically with a solution of a liquid solvent and gas propellant. The device  10  includes a rectangular housing or frame  12  preferably constructed of sheet steel. Details of the housing construction and mechanical elements within the housing are disclosed in U.S. Pat. No. 5,535,790, the disclosure of which is incorporated herein by reference. 
   The device  10  includes a filling head assembly  15  shown in cross-section in  FIG. 3 . The filling head assembly  15  includes a cylindrical body  16  having axially spaced, radially extending round flanges  17  which vertically locate the head assembly in a slot  18  in a horizontal support plate  19  carried in the frame  12 . The body  16  is preferably formed of aluminum and anodized with hard coat type  3 . At an upper end, the body  16  has external threads  21  to couple the body with a cup-like reservoir  22 . The body  16  is formed with a series of bores  23 – 27  coaxial with the body and interconnected so as to allow passage of fluid through the body as described below. 
   A major bore  23  at an upper end of the body  16  forms a cylinder for a piston  28 . A minor bore  24  at the lower end of the piston cylinder bore  23  leads to a valve assembly  29  in an intermediate bore  25 . A shallow bore  26  at the lower end of the intermediate bore  25  receives an O-ring seal  31  for a filling nozzle  32  received in a lower bore  27  and the intermediate bore  25 . 
   The valve assembly  29  includes a seat  33 , a ball  34 , and a compression spring  36  for biasing the ball into sealing contact with the seat. 
   The filling nozzle  32  is a circular, integral body, having as coaxial elements, a main disc-like element  37 , an upwardly extending circular skirt  38 , and a depending hollow projecting pin or injector  39 . The exterior of the skirt  38  is threaded and mates with internal threads at the lower end of the intermediate bore  25 . The O-ring  31  is assembled on the base of the skirt  38  where it joins the main disc  37  and is received in the shallow bore  26  when the nozzle skirt  38  is threaded into the intermediate bore  25  and an upper face of the disc  37  abuts a radial surface at the end of the bore  27 . The disc  37  has a pair of blind holes (not shown), on a common diametral line, in its lower face to enable it to be turned in or out of assembly with the body  16  using a suitable spanner wrench. In assembly, the valve spring  36  and a portion of the ball  34  are received in the interior of the nozzle skirt  38 . A washer-like retaining ring  44 , preferably of metal, is assembled between the upper end of the nozzle skirt  38  and the seat  33  and has a clearance bore to enable the ball  34  to move freely with respect to the seat. 
   The seat  33  has the configuration of an O-ring, i.e. that of a toroid described by the rotation of a circle rotated about an axis lying in the plane of the circle and spaced from it. The seat  33 , is preferably a commercially available product. The seat  33  is formed of a suitable plastic material which is resistant to solvents and chemicals ordinarily used with materials being injected into an aerosol can. Preferably, the seat is constructed of polytetrafluoroethylene (PTFE) such as that marketed under the registered trademark Teflon®. In the illustrated example, the seat  33  is made of PTFE and has a nominal OD of 7/16″ and an ID of ¼ while the valve ball is 17/64″ in diameter. The nozzle disc  37  and injector pin  39  have a common central bore; a cross bore  47  adjacent the lower end of the injector pin  39  intercepts and provides a fluid outlet or exhaust for the bore  46 . 
   A carrier assembly  51  raises and supports an aerosol can  11  to a position for receiving a charge of liquid material from the filling head  15 . The carrier assembly  51  includes a circular support platform  52  and a compression spring  53 . The platform  52  has an inverted round cup shape. At its upper periphery, an end wall  54  of the platform  52  has an annular lip  56  adapted to laterally or radially constrain the bottom of an aerosol can. A pair of spring mounts  57  secure opposite ends of the spring  53 . The spring mounts  57  are relatively short circular bodies having helical grooves on their peripheries that are configured to receive the inside of the end coils of the spring  53  by tightly threading into the same. The mounts  57  are fixed to the underside of the platform  52  and a base  58  of the frame  12  with suitable screws  59 ,  61  in coaxial alignment with the filling head assembly  15 . 
   The relatively large diameter of the spring being, for instance, about 2¼″ in OD and a major fraction of its free length of about 3″, combined with a wire diameter of, for instance, about 0.148″ yields a construction that gives the spring the ability to adequately stabilize the platform  52 , biasing it to a vertical axis orientation coaxial with the filling head. 
   In use, an aerosol can  11  is manually placed on the platform  52  while the can is tilted so that its bottom fits within the lip  56  and its upper or dispensing end accommodates the filling head assembly  15 . The can  11  is manually depressed moving the platform  52  downwardly against the force bias of the spring  53 . When the can  11  is low enough, it is rotated upright and the support or carrier assembly  51  is allowed to lift the can so that its upper end receives a depending alignment collar or skirt  48  on the lower portion of the filling head assembly  15 . When the alignment collar  48  slips into the recess of a cap  50  crimped onto the upper end of the can  11  and thereby laterally locates the upper end of the can, a female valve  66  at a central port  67  on the cap  50  of the can couples with the injector pin or connector  39 . 
   It will be understood that the can loading motion can be manually accomplished with one or both hands of a person operating the device  10  without the need to grasp or manipulate extraneous elements such as levers, knobs and so-forth. With paint or other liquid material in the reservoir  22 , a handle  71  can be operated back and forth to reciprocate the piston  28  in and out of the major bore cylinder  23  to inject the material into the can  11  through the injector pin  39 . An example of a suitable mechanism for driving the piston  28  through the handle  71  is given in aforementioned U.S. Pat. No. 5,535,790. A downward stroke of the piston  28  hydraulically opens the valve assembly  29  by the force of the pressure against the ball  34  which is sufficient to overcome the bias force of the spring  36 . The spring  53  of the carrier assembly  51  is proportioned to hold the can  11  against the filling head assembly  15  with between about seven to ten pounds of force. 
   It will be seen that the spring  53  is the exclusive guide and restraining member for the can support platform  52 . This arrangement avoids slides, guides, or bearing surfaces, or linkages and, thereby, eliminates the risk that dry paint from an accidental spill will prevent operation of the can support carrier assembly  51 . 
   When the desired quantity of liquid material has been injected into the can  11 , the can is removed simply by manually gripping it, depressing it against the force of the spring  53 , and tilting it out from under the filling head assembly  15 . The can  11  is thus released and may be taken away from the filling head assembly and the device  10  altogether. 
   It has been discovered that PTFE is an ideal material for the seat  33 . Besides being chemically inert, this material adapts to the surface of the sealing ball so as to form a reliable seal with the ball. While the reason or reasons are not presently understood, the PTFE seat has virtually eliminated the problem of blow back. This phenomena of blow back occurs occasionally with prior filling devices when the ball is arranged to contact a metal seat surface and course ground pigment or dry paint particles prevent seating of the metal surfaces. The disclosed PTFE O-ring seat, in combination with the valve ball, has a self-purging action which has been discovered to effectively eliminate this blow back phenomena. 
   It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.