Abstract:
A pressure-limiting pump system for pressurizing a vessel, including a plunger terminating in a piston loose-fitting within a cylinder. The piston includes a flange forming the lip of an annular groove in the piston for supporting an O-ring seal. The groove is provided with a plurality of ports terminating in the piston within the cylinder. The O-ring is slidable on the piston groove surface. On the intake stroke, the O-ring moves to uncover the ports, and on the compression stroke, the O-ring moves to cover the ports to seal the compression chamber. When pressure exceeds a predetermined level, further compression causes air to bypass the O-ring and escape from the chamber, thereby limiting system pressure. The pump system may be mounted on-axis or off-axis in a tank sidearm. A handle is secured to the sprayer tank via shoulder inserts and is pivotable out of the way when filling the tank, yet can be locked in position as desired by a shift in pivot position.

Description:
RELATIONSHIP TO OTHER PATENTS AND APPLICATIONS  
       [0001]    The present application claims priority of U.S. Provisional Patent Application Ser. No. 60/474,069, filed May 29, 2003. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to means for producing superatmospheric pressures in closed vessels; more particularly, to pump means for pressurizing a tank; and most particularly, to an improved piston pump sprayer system having internal relief means for preventing over-pressure of a sprayer tank.  
         BACKGROUND OF THE INVENTION  
         [0003]    It is well known in the pumping art to pressurize a closed vessel or tank by using a compressor comprising a piston slidably sealed in a cylinder. Typically, the cylinder is isolated from the tank by a first check valve through which each successive compressive charge from the cylinder enters the tank. The piston is provided with second check valve, such as a variably-covered port through the piston, for drawing air into the cylinder during the intake stroke, and then for closing the port to permit compression of the air during the compression stroke.  
           [0004]    Hand-pumpable sprayers are well-known in the art and are used for home spraying uses such as application of insecticides, fungicides, and fertilizers, as well as in commercial uses such as spraying concrete, curing compounds, and waterproofing. Typically, a pump system including a cylinder, piston, and check valves is disposed through a threaded cap or plug that fits onto or in a port in a sprayer tank, the cylinder extending into the tank after assembly. Generally, the port is also a fill port for adding materials to the tank between spraying operations.  
           [0005]    In many prior art hand-pump sprayers, the sealant between the piston and the cylinder wall defining the second check valve is a skirt formed of a flexible material such as oiled leather and attached to the underside of the piston. The piston itself is loose-fitting in the cylinder. On the intake stroke of the piston, air is readily drawn into the cylinder past the piston and skirt; however, on the compression stroke, the skirt is expanded against the cylinder wall, sealing the annulus around the piston and permitting compression of the charge. In more recent hand-pump sprayers, the piston is sealed against the cylinder wall by a lubricated O-ring, and air is admitted to the cylinder as by a flapper check valve in the piston.  
           [0006]    A problem with prior art hand-pump sprayers is that the piston becomes harder to pump as the tank pressure increases because greater pressure is required in the cylinder to open the first check valve against the accumulated pressure in the tank. This can present a serious problem for persons of limited strength, especially because a last full compression stroke is required to position the plunger for locking (the plunger handle also functions as the carrying handle for the sprayer). Further, it is possible for a strong operator, through persistent pumping, to raise the tank pressure above what is needed, and perhaps even above what is safe.  
           [0007]    What is needed in the art of hand-pumping means for pressurizing vessels is a piston pump having a pressure-limiting bypass relief valve built in such that the pressure the pump can generate is predetermined by the construction of the bypass, thereby permitting relatively easy return of the plunger to its locking position and preventing over-pressuring of the vessel.  
           [0008]    Another problem with prior art sprayers is that the hand-pump system is mounted axially of the sprayer tank through an opening in the tank cap, and the pump handle functions as a carrying handle when the tank cap is secured onto the tank. The pump plunger typically is provided with opposed radial tangs which pass through corresponding slots in the tank cap and are engaged to the underside thereof through a partial-revolution turn of the plunger. With extended use of the sprayer, the tangs can become worn and fail to reliably grip the tank cap, allowing a full sprayer to unexpectedly and undesirably drop down. Some sprayers tanks are provided with a shoulder strap, but a strap is designed for carrying use over a shoulder and makes a cumbersome carrying handle.  
           [0009]    What is needed in the art of hand-pump sprayers is a separate carrying handle for the sprayer tank. What is further needed is an off-axis sidearm for accommodating the hand-pump system independently of the main tank loading port.  
           [0010]    It is a principal object of the present invention to provide easier pumping of a hand-pumped pressure vessel, for example, a tank sprayer.  
           [0011]    It is a further object of the present invention to automatically limit the pressure attainable in a pressure vessel being pressurized by a hand pump.  
           [0012]    It is a still further object of the present invention to provide a means for carrying a hand-pumped pressure vessel independent of the hand-pump system.  
         SUMMARY OF THE INVENTION  
         [0013]    Briefly described, a pressure-limiting hand pump system for pressurizing a vessel includes a pressure cylinder; a first check valve at an inner end of the cylinder for preventing back-flow of pressurized air or material from the vessel into the cylinder; and a plunger terminating in a piston within the cylinder and in a handle outside the vessel. The piston is loose-fitting within the cylinder and includes an annular flange which is also loose fitting, the flange forming the outer lip of an annular groove in the piston for receiving an O-ring which seals against both the piston and the cylinder wall. The groove has a longer axial extent than the diameter of the O-ring, and the portion of the groove adjacent the annular flange is provided with a plurality of ports connecting to passageways terminating in the piston face within the compression chamber. The O-ring is slidable on both the piston groove surface and the cylinder wall. On the intake stroke, the O-ring is moved axially of the piston in a first direction to uncover the ports, thus permitting air to fill the compression chamber. On the compression stroke, the O-ring is moved in the opposite direction to cover the ports and seal against the axial face of the flange, thereby sealing the compression chamber. The ports are so configured, however, that when the pressure in the compression chamber exceeds a predetermined level, further compression causes air to bypass the O-ring and escape from the chamber, thereby limiting the pressure of which the system is capable and allowing the plunger to be placed in the locking position without requiring excessive force in a last compressive stroke of the plunger.  
           [0014]    In a first embodiment of a hand-pump sprayer in accordance with the invention, the hand-pump system is mounted substantially on-axis in the vessel cap for the main loading port of the sprayer tank. In a second and currently preferred embodiment, the hand-pump system is mounted off-axis in a tank sidearm defining a second opening in the vessel apart from the main loading port of the sprayer tank.  
           [0015]    Each of the embodiments preferably includes a carrying handle pivotably mounted to the sprayer tank to facilitate carrying the entire sprayer without resort to using the pump handle. Preferably, the handle is secured to the sprayer tank via shoulder inserts that permit easy variations for storage mounting of various auxiliary components, such as a spray shield and different spray nozzles, without requiring redesign of the basic tank. Preferably, the handle is pivotable to be swung out of the way when filling the tank, yet can be locked in the upright position as desired by a simple shift in pivot position. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0017]    [0017]FIG. 1 is an exploded isometric view from the front of a first embodiment of a hand-pump pressure sprayer in accordance with the invention, having a hand-pump system disposed axially of the tank in a cap for a tank loading port;  
         [0018]    [0018]FIG. 2 is an exploded isometric view from the front of a second embodiment of a hand-pump pressure sprayer in accordance with the invention, having a hand-pump system disposed in a sidearm of the sprayer tank;  
         [0019]    [0019]FIG. 3 is an elevational view of the handle and plunger of the sprayer shown in FIG. 1;  
         [0020]    [0020]FIG. 4 is an enlarged isometric view of the piston shown in FIG. 1;  
         [0021]    [0021]FIGS. 5 and 6 are cross-sectional elevational views of the piston shown in FIG. 4, FIG. 5 showing the position of an O-ring during an intake stroke and FIG. 6 showing the position of an O-ring during a compression stroke;  
         [0022]    [0022]FIG. 7 is an enlarged exploded isometric view of the hand-pump system shown in FIG. 2;  
         [0023]    [0023]FIG. 8 is an isometric view from below of the piston end of the plunger shown in FIGS. 2 and 7;  
         [0024]    [0024]FIG. 9 is a second isometric view of the sprayer shown in FIG. 2, showing use of the handle-mounting shoulder inserts for accommodating mounting of auxiliary components; and  
         [0025]    [0025]FIG. 10 is an isometric view from above of the handle and shoulder inserts shown in FIGS. 2 and 9. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    Referring to FIGS. 1, 3, and  4 , a first embodiment  10  of a self-contained, hand-pumped utility sprayer includes a tank  12  defining a pressure vessel for holding materials to be sprayed, tank  12  having a swivel outlet  14  for attachment to a hose (not shown) for delivering the materials to a desired site. Tank  12  includes an axial port  16  at an upper end defined by a neck  18  having threads  20  formed on an outer surface thereof. The threads preferably are male threads as shown, although female threads on the inside of neck  18  are fully comprehended by the invention. A circular sealing element  22  is captured between the outer end of neck  18  and an annular surface (not visible in FIG. 1) within cap  24  in known fashion to prevent leakage of materials from port  16  when cap  24  is screwed onto neck  18 .  
         [0027]    Cap  24  is provided with a central opening (not visible in FIG. 1) for receiving a plunger  26  of a hand-pump pressurizing system  28 . A tubular compression cylinder  30  is closed at its lower end  32  by a threaded cap  34  provided with an elastomeric check valve  36  as is known in the art and is sealed to cap  24  at its upper end  25 . A first spring  38  is disposed within cylinder  30  for cushioning plunger subassembly  40  at the end of its downwards compression stroke. Subassembly  40  comprises plunger  26  assembled to piston  42  after insertion through cap  24  and retained therein by barbed bayonets  44 . A second spring  46  is provided on plunger  26  for cushioning plunger subassembly  40  at the end of its upwards intake stroke. Cap  24  is preferably provided with a pressure relief valve assembly  48  for relieving residual pressure in tank  12  at the completion of a spraying operation. Plunger  26  is provided with a handle  50  for manually driving plunger subassembly  40  in cylinder  30 .  
         [0028]    Referring now to FIGS. 4, 5, and  6 , piston  42  is formed preferably by injection molding of a suitably durable plastic polymer and comprises an upper chamber  52  and a lower chamber  54  separated by a septum  56 . For convenience, septum  56  extends radially outwards to form a first radial flange  58 . Piston  42  terminates at an upper end in a second flange  60  formed as a spring seat for spring  46  and surrounding an opening  62  for receiving bayonets  44 . Upper chamber  52  is provided with one or more radial passages  64 . Piston  42  terminates at a lower end in a third flange  66  formed as a spring seat for spring  38  and surrounding chamber  54 . Lower chamber  54  is provided with one or more radial passages  68 . Piston  42  is formed such that air may pass between flange  58  and the wall  70  of cylinder  30  during both the intake stroke (FIG. 5) and the compression stroke (FIG. 6).  
         [0029]    Flanges  58 , 66  are spaced apart axially to form an annular channel  72  therebetween for receiving an O-ring  74  (shown in FIGS. 5 and 6; omitted from FIG. 4) for forming a sliding seal between wall  70  and piston  42 . The axial extent of channel  72  is greater than the material diameter of O-ring  74 . Thus, the O-ring in the channel acts as a second check valve for pump system  28 . When piston  42  is raised within cylinder  30  as in the intake stroke, as shown in FIG. 5, O-ring  74  is urged away from flange  58  by friction with wall  70 , allowing air to enter cylinder  30  by bypassing piston  42  via the periphery of flange  58  and passages  68 . When piston  42  is lowered within cylinder  30  as in the compression stroke, as shown in FIG. 6, O-ring  74  is urged into contact with flange  58 , thus sealing flange  58  against wall  70 .  
         [0030]    In accordance with the invention, O-ring  74  and channel  72  may be sized without undue experimentation to provide a relationship therebetween wherein air being compressed by piston  42  within cylinder  30  is able to escape by forcing O-ring  74  away from wall  70  and/or flange  58 . For example, use of a 0.025 inch diametric interference between the o-ring  74  and the wall  70  would work well. Thus, the piston can be configured to provide pressure relief means at a predetermined pressure, as desired, within cylinder  30 . In an alternate embodiment one or move radial grooves  61  may be scribed in axial face  59  of flange  58  to permit a controlled amount air to escape past O-ring  74  when air is being compressed by piston  42  to provide pressure relief means at a predetermined pressure.  
         [0031]    Referring to FIGS. 2, 7, and  8 , a second embodiment  10 ′ of a self-contained, hand-pumped utility sprayer includes a tank  12 ′ defining a pressure vessel for holding materials to be sprayed, tank  12 ′ having a swivel outlet  14 ′ for attachment to a hose (not shown) for delivering the materials to a desired site. Tank  12 ′ includes an axial port  16 ′ on an upper end defined by a neck  18 ′ having threads  20 ′ formed on an outer surface thereof. The threads preferably are male threads as shown, although female threads on the inside of neck  18 ′ are fully comprehended by the invention. A circular sealing element  22 ′ is captured between the outer end of neck  18 ′ and an annular surface (not visible in FIG. 1) within cap  24 ′ in known fashion to prevent leakage of materials from port  16 ′ when cap  24 ′ is screwed onto neck  18 ′.  
         [0032]    Cap  24 ′ is provided with a central opening  27  for receiving a pressure relief valve assembly  48  for relieving residual pressure in tank  12 ′ at the completion of a spraying operation.  
         [0033]    Tank  12 ′ includes a sidearm  80  having a threaded port  82  for receiving a hand-pump pressurizing system  28 ′. Sidearm  80  and port  82  define a second port in tank  12 ′ additional to first port  16 ′. Thus port  16 ′ may function as a materials loading port without requiring that hand-pump pressurizing system  28 ′ be disassembled from tank  12 ′ as in the prior art wherein the pressurizing system is disposed axially through the main loading port cap, as in embodiment  10 . A tubular compression cylinder  30 ′ is closed at its lower end  32 ′ by a threaded cap  34 ′ provided with an elastomeric check valve  36 ′ as is known in the art. A first spring (not visible in FIG. 2) may be disposed within cylinder  30 ′ for cushioning plunger subassembly  40 ′ at the end of its downwards compression stroke. Subassembly  40 ′ comprises a plunger  26 ′ integral with a piston  42 ′ formed preferably by injection molding of a suitably durable plastic polymer. Plunger  26 ′ is provided with a handle  50 ′ for manually driving plunger subassembly  40 ′ in cylinder  30 ′.  
         [0034]    Piston  42 ′ (FIG. 8) comprises a first radial flange  58 ′ and a second radial flange  66 ′ provided with one or more passages  68 ′. Piston  42 ′ is formed such that air may pass between flange  58 ′ and the wall of cylinder  30 ′ during both the intake stroke and the compression stroke. Flanges  58 ′, 66 ′ are spaced apart axially to form an annular channel  72 ′ therebetween for receiving an O-ring  74 ′ (shown in FIGS. 2 and 7; omitted from FIG. 8) for forming a sliding seal between the wall of cylinder  30 ′ and piston  42 ′. The axial extent of channel  72 ′ is greater than the material diameter of O-ring  74 ′. Thus, the O-ring in the channel acts as a second check valve for pump system  28 ′. When piston  42 ′ is raised within cylinder  30 ′ as in the intake stroke, O-ring  74 ′ is urged away from flange  58 ′ by friction with the cylinder wall, allowing air to enter cylinder  30 ′ by bypassing piston  42 ′ via the periphery of flange  58 ′ and passages  68 ′. When piston  42 ′ is lowered within cylinder  30 ′ as in the compression stroke, O-ring  74 ′ is urged into contact with flange  58 ′, thus sealing flange  58 ′ against the cylinder wall.  
         [0035]    In accordance with the invention, O-ring  74 ′ and channel  72 ′ may be sized without undue experimentation to provide a relationship therebetween wherein air being compressed by piston  42 ′ within cylinder  30 ′ is able to escape by forcing O-ring  74 ′ away from the wall of cylinder  30 ′ and/or flange  58 ′. Thus, the piston can be configured to provide pressure relief means at a predetermined pressure, as desired, within cylinder  30 ′. Alternatively, as shown in FIG. 8, one or move radial grooves  61 ′ may be scribed in axial face  59 ′ of flange  58 ′ to permit a controlled amount air to escape past O-ring  74 ′ when air is being compressed by piston  42 ′ to provide pressure relief means at a predetermined pressure.  
         [0036]    Pressurizing system  28 ′ further comprises a guide element  84 , having an anti-rotation snap tab  86  for engaging with a detent  88  in the outer end of cylinder  30 ′. Cylinder  30 ′ includes a shoulder  90  for sealingly engaging threaded neck  92  of sidearm  80 . A threaded closure ring  94  secures system  28 ′ to neck  92 . Preferably, system  28 ′ further includes a stirrup ring  96  which may snap onto closure ring  94 . Ring  96  includes one or more open stirrups  98 , 100 , which may be of different sizes, for use as storage sites for the sprayer&#39;s hose and/or wand apparatus (not shown).  
         [0037]    Referring to FIGS. 2, 9, and  10 , sprayer embodiment  10 ′ may be further provided with a rotatable handle system  102  comprising first and second shoulder inserts  104   a , 104   b  which may or may not be mirror images of one another. Tank  12 ′ includes recesses  106   a , 106   b  for receiving the shoulder inserts. Inserts  104   a , 104   b  are secured into recesses  106   a , 106   b  by any suitable securing means, and preferably are releasably secured by one or more bishop snaps  108  formed in the inserts and insertable into blind bores  110  formed in tank  12 ′. A reason for providing shoulder inserts rather than engaging handle  112  directly into tank  12 ′ is that the configuration of the inserts may be readily adapted to provide special features  113  for removable storage of various auxiliary attachments and components, such as a spray shield  114 , alternative nozzles (not shown), etc. as may be provided with various models of sprayer, without requiring expensive alteration to the mold for the common tank  12 ′.  
         [0038]    Handle system  102  preferably is configured to permit more than one handle position and function. Handle  112  is provided with opposed bishop-type studs  116 , each including a split flange  118 . Shoulder inserts  104   a , 104   b  each include an opening  120  that is elongate in the axial direction of tank  12 ′. Studs  116 , when inserted into openings  120 , are pivotably retained therein by flanges  118 , allowing handle  112  to extend upwards as shown in FIG. 2 for carrying of sprayer  10 ′ or to be folded to one side (not shown) for access to cap  24 ′ and port  16 ′.  
         [0039]    Further, each shoulder insert is provided with a flush-mounted saddle element  122  comprising a short extension  124 , a long extension  126  extending generally in the axial direction of tank  12 ′, and a saddle portion  128  in between. Handle  112  is provided with opposed inwardly-extending tangs  130  positioned on handle  112  such that when studs  116  are urged to an upward extreme in openings  120  the tangs can pass short extensions  124  but cannot pass long extensions  126 .  
         [0040]    These relationships confer the following benefits:  
         [0041]    a) when the handle is released after being used to carry sprayer  10 ′, tangs  130  come to rest on saddle portions  128  between extensions  124 , 126 ; thus the handle is maintained in an upright position by extensions  124 , 126 , to be easily re-grasped by a user;  
         [0042]    b) when the handle is raised such that tangs  130  can clear short extensions  124 , the handle then may be pivoted past pump assembly  28 ′ to permit access to cap  24 ′ and port  16 ′ and to maintain access to, and servicing of, pump assembly  28 ′; and  
         [0043]    c) when the handle is re-grasped in the upright position, long extensions  126  and tangs  130  prevent handle  112  from swinging past an upright position, thus preventing tank  12 ′ from undesirably swinging against the legs of a user while the sprayer  10 ′ is being carried.  
         [0044]    While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.