Abstract:
An apparatus is provided for use with a device for dispensing fluid from a container with an open end and a closed end. A follower is movably disposed in the container and fluid is held between the follower and the open end of the container. An air inlet opening is provided between the follower and the closed end of the container. The apparatus comprises a housing defining a piston chamber, a piston disposed for reciprocal movement in the chamber and an actuator movably mounted to the housing for reciprocating the piston. The housing has an air inlet duct, an air outlet duct, a fluid inlet duct and a fluid outlet duct, all of which open into the chamber. The housing sealingly mounts to the open end of the container such that the interior of the container is in fluid communication with the fluid inlet duct. The piston sealingly engages the chamber walls at two longitudinally spaced locations for dividing the chamber into a first volume and a second volume. The air inlet and air outlet ducts open into the first volume and the fluid inlet and fluid outlet ducts open into the second volume. The piston forces air through the air outlet duct and fluid through the fluid outlet duct when it moves into the chamber and draws fluid into the chamber through the fluid inlet duct and air into the chamber through the air inlet duct when it moves out of the chamber.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates generally to a hand-held device for dispensing a fluid, and more particularly to a device that includes an integral air delivery system for dispensing the fluid.  
           [0002]    Hand-held devices are used extensively for dispensing fluids, such as those for use in automobile maintenance. Automotive fluids range from those which are light and easy to move, such as air and water, to heavy, high viscosity fluids such as oil, grease and the like. The latter demand high pumping pressure to achieve even moderately adequate flow rates.  
           [0003]    Hand-held devices for delivering high viscosity fluids such as grease, or grease guns, are well known. Grease guns generally include a head and a lubricant-containing metal cylinder removably attached to the head. Lubricant is contained in the cylinder either in bulk or in lubricant cartridges loaded into the cylinder. A manually actuated dispensing mechanism associated with the gun head is used for dispensing the lubricant contained in the cylinder. The dispensing mechanism operates to pressurize the cylinder and force lubricant toward an outlet hose attached to the head of the gun. For this purpose, a plunger is disposed in the cylinder to compress the lubricant. Compressive force is supplied by a compression spring housed between the plunger and the closed distal end of the cylinder. Alternatively, the pressure is applied via the use of compressed air, supplied from an external source, that is transported into the rear of the cylinder behind the plunger.  
           [0004]    A significant drawback of conventional grease guns is the difficulty of reloading lubricant into the spent cylinder. In a cartridge-loaded grease gun, for example, the user must detach the metal cylinder from the head of the gun, remove the spent lubricant cartridge from the cylinder, pull back the plunger against the force of the spring using an external handle provided for that purpose, lock the plunger in place at the rear of the cylinder, remove the cover on the replacement lubricant cartridge, place the replacement lubricant cartridge in the cylinder, reattach the cylinder to the gun head and release the plunger for applying pressure to the lubricant in the cartridge. Reloading a grease gun is thus a relatively cumbersome process. In addition, because of the multiple instances in which the user is exposed to lubricant in the process, reloading is invariably a messy endeavor.  
           [0005]    Another drawback of the conventional grease gun is that it is often difficult for the user to determine the type and amount of lubrication loaded in the gun. The user often must dispense a sample amount of lubricant from the gun to determine the specific type of lubricant contained therein. Further, it is difficult, without removing the lubricant cylinder from the grease gun head, to determine the amount of lubricant remaining in the cylinder.  
           [0006]    A further drawback of the typical grease gun is the cost associated with its manufacture. Many of the grease guns currently available require numerous parts for their manufacture and operation, the majority of the parts being composed of metal. The use of metal for these parts, including the lubricant cylinder, significantly adds to the cost of manufacturing the gun.  
           [0007]    For the foregoing reasons, there is a need for a hand-held fluid dispensing apparatus that is easy to load and that can be loaded without excess mess. Ideally, the new hand-held fluid dispensing apparatus is inexpensive to manufacture and easy to use for various lubricating and other fluid dispensing jobs.  
         SUMMARY OF INVENTION  
         [0008]    According to the present invention, an apparatus is provided for use with a device for dispensing fluid from a container for holding fluid. The container has an open first end and a closed second end. A follower is movably disposed in the container and the follower sealingly engages the inner surface of the container so that the fluid is held between the follower and the open first end of the container. The container has an air inlet opening between the follower and the closed second end of the container. The apparatus for dispensing fluid from the container comprises a housing defining a piston chamber closed at at least one end, a piston disposed in the piston chamber and an actuator mounted to the housing. The housing has an air inlet duct, an air outlet duct adapted to be connected to the air inlet opening in the container, a fluid inlet duct and a fluid outlet duct, all of the ducts opening into the piston chamber. The housing is adapted to be sealingly mounted to the open first end of the container such that the interior of the container is in fluid communication with the fluid inlet duct. The piston is disposed for reciprocal movement in the piston chamber. The periphery of the piston disposed in the piston chamber sealingly engages the chamber walls at two longitudinally spaced locations for dividing the piston chamber into a first fluid-tight volume between the two sealingly engaged positions and a second fluid tight volume between the second sealingly engaged position and the closed end of the piston chamber. The air inlet and air outlet ducts open into the first volume and the fluid inlet and fluid outlet ducts open into the second volume. When the piston moves into the piston chamber, the piston forces air in the piston chamber through the air outlet duct and fluid in the piston chamber through the fluid outlet duct. When the piston moves out of the piston chamber, the piston draws fluid into the piston chamber through the fluid inlet duct and air into the piston chamber through the air inlet duct. The actuator is movably mounted to the housing and operatively connected to the piston and reciprocates the piston when moved relative to the housing.  
           [0009]    Also according to the present invention, an apparatus for dispensing fluid is provided including a housing defining a piston chamber closed at at least one end, a piston disposed in the piston chamber, an actuator mounted to the housing, a container for holding fluid, a follower disposed in the container and an air delivery tube. The housing has an air inlet duct, an air outlet duct, a fluid inlet duct and a fluid outlet duct, all of the ducts opening into the piston chamber. The piston is disposed for reciprocal movement in the piston chamber. The periphery of the piston sealingly engages the chamber walls at two longitudinally spaced locations for dividing the piston chamber into a first fluid-tight volume between the two sealingly engaged positions and a second fluid tight volume between the second sealingly engaged position and the closed end of the piston chamber. The air inlet and air outlet ducts open into the first volume and the fluid inlet and fluid outlet ducts open into the second volume. When the piston moves into the piston chamber, the piston forces air in the first volume of the piston chamber through the air outlet duct and fluid in the second volume of the piston chamber through the fluid outlet duct. When the piston moves out of the piston chamber, the piston draws air into the first volume of the piston chamber through the air inlet duct and fluid into the second volume of the piston chamber through the fluid inlet duct. The actuator is movably mounted to the housing and operatively connected to the piston through an opening in the housing and reciprocates the piston when moved relative to the housing. The container has an open first end and a closed second end. The open first end of the container is sealingly mounted to the housing such that the interior of the container is in fluid communication with the fluid inlet duct of the housing. A follower is movably disposed in the container and the periphery of the follower sealingly engages the inner surface of the container so that the fluid is held between the follower and the open first end of the container. An air delivery tube is connected at one end with the air outlet duct and opens at the other end into the container between the closed second end of the container and the follower. The air delivery tube delivers air between the closed second end of the container and the follower upon movement of the piston into the piston chamber. The reciprocation of the piston in the piston chamber increases the air pressure in the closed second end of the container. This increase in air pressure forces the follower to move axially relative to the container toward the open first end of the container, pushing fluid through the fluid inlet duct into the second volume of the piston chamber.  
           [0010]    Further, according to the present invention, a fluid dispensing apparatus is provided comprising a housing defining a piston chamber closed at at least one end, a piston disposed in the piston chamber, an actuator mounted to the housing, a container, a fluid disposed in the container, a follower disposed in the container and an air delivery tube. The housing has an air inlet duct, an air outlet duct, a fluid inlet duct and a fluid outlet duct, all of the ducts opening into the piston chamber. The piston is disposed for reciprocal movement in the piston chamber. The periphery of the piston sealingly engages the chamber walls at two longitudinally spaced locations for dividing the piston chamber into a first fluid-tight volume between the two sealingly engaged positions and a second fluid tight volume between the second sealingly engaged position and the closed end of the piston chamber. The air inlet and air outlet ducts open into the first volume and the fluid inlet and fluid outlet ducts open into the second volume. When the piston moves into the piston chamber, the piston forces air in the first volume of the piston chamber through the air outlet duct and the fluid in the second volume of the piston chamber through the fluid outlet duct. When the piston moves out of the piston chamber, the piston draws air into the first volume of the piston chamber through the air inlet duct and fluid into the second volume of the piston chamber through the fluid inlet duct. The actuator is movably mounted to the housing and operatively connected to the piston through an opening in the housing and reciprocates the piston when moved relative to the housing. The container has an open first end and a closed second end. The open first end of the container is sealingly mounted to the housing such that the interior of the container is in fluid communication with the fluid inlet duct. The follower is movably disposed in the container and the periphery of the follower sealingly engages the inner surface of the container so that the fluid is held between the follower and the open first end of the container. The air delivery tube is connected at one end with the air outlet duct and opens at the other end into the container between the closed second end of the container and the follower. The air delivery tube delivers air between the closed second end of the container and the follower upon movement of the piston into the piston chamber. The reciprocation of the piston in the piston chamber increases the air pressure in the closed second end of the container. This increase in air pressure forces the follower to move axially relative to the container toward the open first end of the container, pushing fluid through the fluid inlet duct into the second volume of the piston chamber. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]    For a more complete understanding of the present invention, reference should now be had to the embodiments shown in the accompanying drawings and described below. In the drawings:  
         [0012]    [0012]FIG. 1 is a side elevation view of a fluid dispensing apparatus according to the present invention;  
         [0013]    [0013]FIG. 2 is a longitudinal cross-section of the fluid dispensing apparatus shown in FIG. 1;  
         [0014]    [0014]FIG. 3 is side elevation view of a piston for use in a fluid dispensing apparatus according to the present invention;  
         [0015]    [0015]FIG. 4 is an exploded perspective view of a container, an air delivery tube and a follower for use in a fluid dispensing apparatus according to the present invention;  
         [0016]    [0016]FIG. 5 is a longitudinal cross-section of the fluid dispensing apparatus shown in FIG. 2 with the lever at the end of a fluid delivery stroke; and  
         [0017]    [0017]FIG. 6 is a longitudinal cross-section of the fluid dispensing apparatus shown in FIG. 2 with the lever returning to the position shown in FIG. 2. 
     
    
     DETAILED DESCRIPTION  
       [0018]    Certain terminology is used herein for convenience only and is not to be taken as a limitation on the invention. For example, words such as “upper,” “lower,” “left,” “right,” “horizontal,” “vertical,” “upward,” and “downward” merely describe the configuration shown in the FIGs. Indeed, the components may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise.  
         [0019]    Referring now to the drawings, wherein like reference numerals designate corresponding or similar elements throughout the several views, an embodiment of a fluid dispensing apparatus according to the present invention is shown in FIG. 1 and generally designated at  10 . The apparatus  10  comprises a head  12 , a container  14 , a pistol-grip  16  including a pivoting lever  18  and a handle  20  rigidly attached to the head  12 , and a reciprocating piston  22  connected at one end to the lever  18  and extending into the head  12 . A spring  24  surrounding the piston  22  is positioned between the head  12  and the lever  18  for biasing the lever  18  and piston  22  away from the head  12 . A push-button air pressure release valve  26  of the type typically used in the art extends through the head  12  for the purpose of relieving air pressure within the device  10 .  
         [0020]    When a user desires to dispense fluid, the user holds the pistol grip  16  with the palm of the hand on the lever  18  and fingers around the handle  20 . Applying pressure moves the lever  18  toward the handle  20  and drives the piston  22  into the head  12  for pumping fluid from an outlet conduit  28 , as will be described below. The structure and operation of the pistol-grip  16  is described in U.S. Pat. No. 5,277,339, the contents of which are hereby incorporated by reference. Accordingly, a detailed explanation of the pistol-grip  16  is deemed unnecessary for understanding of the present invention by one of ordinary skill in the art. However, it is understood that any pistol-grip or lever-type actuating mechanism may be used to reciprocate the piston  22  for dispensing lubricant in accordance with the present invention. Moreover, although a rigid pipe is depicted as the outlet conduit  28  in the FIGS., a flexible outlet hose or any other suitable conduit may be used.  
         [0021]    As shown in FIG. 2, a piston chamber  30  is formed inside the head  12 . The piston chamber  30  is open at one end of the head  12  for receiving the piston  22 . A first portion  32  of the piston chamber  30  proximal the open end is wider in diameter than a second distal portion  34  of the piston chamber  30 . The piston  22  (FIG. 3) has a wider intermediate portion  36  which fits within the first portion  32  of the piston chamber  30 . As seen in FIG. 2, the piston  22  extends partially into the second portion  34  of the piston chamber  30  when the fluid dispensing apparatus  10  is not in use. An O-ring  38  is attached in a peripheral groove  40  on the wider intermediate portion  36  of the piston  22  to sealingly engage the walls of the first portion  32  of the piston chamber  30 . Similarly, an O-ring  42  is attached in a peripheral groove  44  adjacent the distal end  46  of the piston  22  to sealingly engage the walls of the second portion  34  of the piston chamber  30 . The O-rings  38 ,  42  attached to the piston  22  provide fluid-tight separation of the piston chamber  30  while allowing the piston  22  to reciprocate linearly relative to the walls of the piston chamber  30  due to material deformation of the O-rings  38 ,  42 .  
         [0022]    The head  12 , pistol grip  16  and piston  22  are preferably made of metal or of a synthetic polymeric material. Suitable synthetic polymeric materials are those that are rigid, including but not limited to, polycarbonate, polyethylene terephthalate (PET), high density polyethylene (HDPE) and the like. Nevertheless, any material of sufficient strength to withstand the forces the fluid dispensing apparatus  10  may encounter in use may be used. Moreover, the use of the O-rings  38 ,  42  attached to the piston  22  eliminate the need for a precision cut piston chamber  30  and, thus, allows for the head  12  to be inexpensively manufactured. It is understood that the scope of the invention is not intended to be limited by the materials listed herein, but may be carried out using any materials that allow the construction and operation of the described fluid dispensing apparatus  10 .  
         [0023]    An air inlet duct  48  extends through the front wall of the head  12  and opens into the first portion  32  of the piston chamber  30 . An elastomeric ball check valve  50  positioned in the air inlet duct  48  permits air to flow only from the ambient into the piston chamber  30 . An air outlet duct  52  extends from the first portion  32  of the piston chamber  30  and through the rear wall of the head  12 . An elastomeric ball check valve  54  positioned in the air outlet duct  52  permits air to flow only out of the first portion  32  of the piston chamber  30 . A fluid inlet duct  56  extends through the rear wall of the head  12  and opens into the second portion  34  of the piston chamber  30 . A metal ball check valve  58  positioned in the fluid inlet duct  56  permits fluid to flow only into the second portion  34  of the piston chamber  30 . A fluid outlet duct  60  extends from the second portion  34  of the piston chamber  30  and through the front wall of the head  12 . A metal ball check valve  62  positioned in the fluid outlet duct  60  permits fluid to flow only out of the second portion  34  of the piston chamber  30 . The fluid outlet duct  62  is adapted to threadably receive the outlet conduit  28 .  
         [0024]    Although ball check valves are shown, it is understood that other suitable check valves, such as flap check valves and the like, may be used. The check valves can be manufactured from metal, plastic, elastomeric material, or any other suitable material. Preferably, the valves  50 ,  54  positioned in the air inlet and outlet ducts  48 ,  52  are formed from an elastomeric material. Because petroleum based fluids may not interact well with elastomeric material, the valves  58 ,  62  positioned in the lubricant inlet and outlet ducts  56 ,  60  are preferably composed of metal. Alternatively, the air and fluid outlet ducts  52 ,  60  can be longitudinally spaced toward the closed end of the piston chamber  30  relative to the air and fluid inlet ducts  48 ,  56 , respectively. Thus, as the piston  22  moves into the piston chamber  30 , the periphery of the piston  22  will seal the air and fluid inlet ducts  48 ,  56 . In this arrangement, check valves need not be provided in the air and fluid inlet ducts  48 ,  56 .  
         [0025]    The rear of the head  12  comprises a circular threaded flange  64  defining a recess  66 . The threaded flange  64  is preferably composed of the same material used for the head  12 . However, it is contemplated that the threaded flange  64  could be composed of a material different from that of the head  12  as long as the chosen material permits the container  14  to sealingly engage the circular threaded flange  64  of the head  12 , as will be described below.  
         [0026]    Referring to FIG. 4, the container  14  has an open first end  68  and a closed second end  70  and is adapted for containing fluid  72  to be dispensed. An elongated hollow air delivery tube  74  and a cup-shaped follower  76  are disposed inside the container  14 . An O-ring  78  is seated in a peripheral groove  80  on the outside of the follower  76  to ensure that the follower  76  sealingly engages the inner wall of the container  14 . At the center of the follower  76  is an opening  82  designed to permit the air delivery tube  74  to slidingly pass through the follower  76 . The container  14 , hollow air delivery tube  74 , and follower  76  are preferably made of a metal or synthetic polymeric material. Suitable synthetic polymeric materials are those that are rigid, including but not limited to, polycarbonate, polyethylene terephthalate (PET), high density polyethylene (HDPE) and the like. Nevertheless, any material of sufficient strength to withstand the forces the fluid dispensing apparatus  10  may encounter in use may be used.  
         [0027]    The open first end  68  of the container  14  is externally threaded for coupling with the circular threaded flange  64  on the head  12 . As best seen in FIG. 2, an O-ring  84  is seated in a groove  86  in the flange  64  for sealing the connection between the head  12  and the container  14 . The air delivery tube  74  connects at one end to the air outlet duct  52  in the head  12  and extends longitudinally from the open first end  68  of the container  14  to the closed second end  70  of the container  14 . An O-ring  88  is seated in a groove  90  inside the air outlet duct  52  to sealingly engage the air delivery tube  74 . An O-ring  92  is contained within the opening  78  of the follower  76  to ensure that the area between the follower  76  and the air delivery tube  74  is sealed. The thickness of the peripheral wall  94  of the follower  76  tapers rearwardly to promote low friction movement of the follower  76  relative to the container  14  and to allow some deflection, as necessary, to counteract any irregularities in the shape of the container  14 . Thus, the volume defined by the closed end  70  of the container  14  and the follower  76  is sealingly separated from the volume on the other side of the follower  76  at the open end  68  of the container  14 . The fluid  72  to be dispensed is placed in the container  14  between the follower  76  and the open first end  68  of the container  14 . It is anticipated that a wide variety of fluids may be dispensed using the apparatus  10  of the present invention, including, but not limited to, for example, lubricants such as grease and other high viscosity fluids or semi-solid materials that require high pumping pressure to achieve adequate flow rates such as caulk, glue, cake frosting and the like.  
         [0028]    In use, the lever  18  attached to the head  12  is manually actuated toward the handle  20 , moving the piston  22  into the piston chamber  30  in the head  12  as illustrated in FIG. 5. The movement of the wider intermediate portion  36  of the piston  22  in this direction forces air from the first portion  32  of the piston chamber  30  through the air outlet duct  52  and air delivery tube  74  to the space between the follower  76  and the closed end  70  of the container  14 . The increase in air pressure forces the follower  76  to the left (as seen in FIG. 5) in the container  14  and thereby forces the fluid  72  towards the open first end  68  of the container  14 . Similarly, the movement of the distal end  46  of the piston  22  farther into the second portion  34  of the piston chamber  30  forces fluid in the second portion  34  of the piston chamber  30  through the fluid outlet duct  60  where it is emitted from the outlet conduit  28 .  
         [0029]    As illustrated in FIG. 6, when pressure on the lever  18  is released, the spring  24  surrounding the piston  22  forces the lever  18  away from the handle  20 , moving the piston  22  out of the piston chamber  30  to its original position (as seen in FIG. 2). A vacuum is created in the piston chamber  20  by the movement of the piston  22 , drawing fluid through the fluid inlet duct  56  into the second portion  34  of the piston chamber  30  and air from the ambient through the air inlet duct  48  into the first portion  32  of the piston chamber  30 . As described above, the O-ring  38  on the wider intermediate portion  36  of the piston  22  prevents air entering the first portion  32  of the piston chamber  30  from passing out of the open end of the piston chamber  30  and the O-ring seal  42  on the distal end  46  of the piston  22  prevents air from entering into the second portion  34  of the piston chamber  30 .  
         [0030]    When the fluid  72  in the container  14  has been fully dispensed, or when the user desires to dispense a different fluid, the user must reload the apparatus  10 . To reload, the user removes the container  14  from the threaded flange  64  on the head  12  and detaches the air delivery tube  74  in the container  14  from the air outlet duct  52 . The user then attaches a different container  14  and its components to the head  12  by inserting the air delivery tube  74  into the air outlet duct  52  and fastening the new container  14  to the head  12 .  
         [0031]    In an alternative embodiment of the apparatus  10 , the air delivery tube  74  is permanently attached to the air outlet duct  52 . In this embodiment, when the user removes the container  14  from the head  12 , the air delivery tube  74  slides out of the follower  76 . When the user then attaches a different container  14  to the head  12 , the user must insert the air delivery tube  74  through the opening  82  in the follower before fastening the container  14  to the head  12 .  
         [0032]    It is contemplated that when an inexpensive material is used for the container  14  and its components, the user, upon dispensing all of the fluid  72  contained therein, may dispose of the entire container  14  and its contents when spent. This serves to make the process of reloading the apparatus  10  significantly easier and cleaner. Moreover, the use of an easily removable container  14  also allows for different sizes of containers  14  to be utilized with the device  10 . Thus, so long as the air pressure generated by the piston is sufficient to pressurize a predetermined volume of fluid in the container  14 , the user can utilize different sized containers  14  adapted to attach to the head  12  containing different volumes of fluid  72  depending on the extent of the job required. Further, at least a portion of the container  14  may be translucent so that the user can see through the container  14  to determine the type and amount of fluid  72  contained therein.  
         [0033]    In an embodiment of the fluid dispensing apparatus where the head  12 , pistol grip  16 , and reciprocating piston  22 , are also made of an inexpensive material, the entire apparatus  10  can be manufactured for low cost. The use of an inexpensive material for the all of the components would, thus, allow for the user, upon dispensing all of the fluid  72  contained therein, to dispose of the entire apparatus  10  without having to ever be exposed to the fluid  72  in the container.  
         [0034]    Although the present invention has been shown and described in considerable detail with respect to only a few exemplary embodiments thereof, it should be understood by those skilled in the art that we do not intend to limit the invention to the embodiments since various modifications, omissions and additions may be made to the disclosed embodiments without materially departing from the novel teachings and advantages of the invention, particularly in light of the foregoing teachings. For example, the air delivery tube for transporting air from the head to the space between the follower and the closed second end of the container could be external from the container. Accordingly, we intend to cover all such modifications, omission, additions and equivalents as may be included within the spirit and scope of the invention as defined by the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a crew may be equivalent structures.