Abstract:
A manually operated liquid foaming dispenser is attached to the top of a container of liquid and is manually reciprocated to dispense the liquid from the container as a foam. The dispenser includes a liquid pump chamber and an air pump chamber that respectively pump liquid and air under pressure to a discharge passage of the pump where the liquid and air are mixed, generating the foam dispensed from the dispenser. The air pump chamber has a tube valve controlling the discharge of air from the air pump to the discharge passage, and the air pump chamber is charged with air by opening the air pump chamber to the exterior environment of the dispenser.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention pertains to a manually operated liquid foaming dispenser. Specifically, the invention pertains to a manually operated trigger sprayer that is attached to the top of a bottle of liquid and has a manually manipulated trigger that is reciprocated to dispense the liquid from the container as a foam. The trigger sprayer includes a liquid pump chamber and an air pump chamber that respectively pump liquid and air under pressure to a discharge passage of the sprayer where the liquid and air are mixed, generating the foam dispensed from the sprayer. 
     (2) Field of the Invention 
     Manually operated liquid dispensers that dispense liquid as a foam are known in the prior art. Common among these types of dispensers are manually operated trigger sprayers that pump liquid from a bottle container attached to the trigger sprayer and dispense the liquid as a foam that is discharged from the trigger sprayer. The dispensing nozzle of this type of trigger sprayer typically discharges the liquid as a spray toward an obstruction that is vented to the atmosphere. The spray hitting the obstruction mixes the liquid spray with the air of the atmosphere producing the foam that is discharged from the trigger sprayer. 
     The typical trigger sprayer that discharges a foam is constructed of a sprayer housing containing a pump chamber, a liquid supply passage, and a liquid discharge passage. The liquid supply passage communicates the pump chamber with the liquid contained in the container attached to the trigger sprayer. A pump piston is mounted in the pump chamber for reciprocating movement between charge and discharge positions. A trigger is attached to the sprayer housing and is connected to the pump piston for moving the pump piston. The pump chamber also communicates with the liquid discharge passage which extends from the pump chamber to the discharge nozzle of the trigger sprayer. 
     A first check valve assembly is positioned between the pump chamber and the liquid supply passage. The first check valve allows liquid to travel through a dip tube and the liquid supply passage into the pump chamber when the pump piston is moved to the charge position, and prevents the reverse flow of liquid from the pump chamber when the pump piston is moved to the discharge position. A second check valve is usually positioned in the discharge passage between the pump chamber and the discharge nozzle. The additional check valve assembly allows the flow of liquid from the pump chamber through the discharge passage to the discharge nozzle when the pump piston is moved to the discharge position, but prevents the reverse flow of liquid and/or air when the pump piston is moved to the charge position. 
     The basic construction of the foaming liquid trigger sprayer described above is well suited for dispensing liquids where the desired foaming of the liquid is marginal, for example in dispensing foaming liquid kitchen cleaners or bathroom cleaners. However, the foaming trigger sprayers cannot produce a more dense foam such as that of shaving cream. 
     To produce a more dense foam such as that of shaving cream from a liquid dispenser requires that both the liquid and air being mixed by the dispenser be under pressure. This requires that the manually operated foaming dispenser include both a liquid pump chamber and an air pump chamber. The addition of the air pump chamber to the manually operated dispenser increases the number of component parts of the dispenser. The air pump chamber must also have an air pump piston that moves between the charge and discharge positions in the air pump chamber to draw air into the chamber and force air under pressure from the chamber. In addition, the air pump chamber must also have a check valve assembly that allows the air of the exterior environment of the dispenser to flow into the air pump chamber when the air pump piston is moved to the charge position and prevents the flow of air from the air pump chamber to the exterior environment when the air pump piston is moved to the discharge position. A second check valve assembly is also needed to control the flow of pressurized air from the air pump chamber to the discharge passage when the air pump piston is moved to the discharge position, and to prevent the reverse flow of air from the discharge passage to the air pump chamber when the air pump piston is moved to the charge position. These additional component parts required by this type of liquid foaming dispenser significantly increase manufacturing costs. 
     SUMMARY OF THE INVENTION 
     The air foaming trigger sprayer of the present invention reduces manufacturing costs by reducing the number of separate component parts that are assembled into the trigger sprayer. More specifically, the trigger sprayer of the invention is constructed with a triple valve member, replacing three separate valves of prior art air foaming sprayers with a single member that performs the functions of three prior art valves. 
     The trigger sprayer has a sprayer housing that is similar to the sprayer housings of prior art trigger sprayers in that it comprises a pump chamber, a vent chamber, a liquid discharge passage and a liquid supply passage. A connector cap attaches the trigger sprayer housing to a separate bottle containing a liquid to be dispensed by the trigger sprayer. A portion of the liquid discharge passage and a portion of the liquid supply passage are formed as a single continuous passage that extends vertically upwardly through the sprayer housing from the bottom of the sprayer housing. The top of the continuous vertical passage communicates with the remainder of the discharge passage that extends to the nozzle assembly on the sprayer housing. 
     In addition, an air pump chamber is provided on the sprayer housing. The air pump chamber surrounds the liquid pump chamber. The coaxial arrangement of the liquid pump chamber and the air pump chamber give the air foaming trigger sprayer a compact construction. 
     A liquid pump piston is received in the liquid pump chamber for reciprocating movement between charge and discharge positions of the liquid pump piston in the liquid pump chamber. In addition, an air pump piston is mounted on the liquid pump piston and is received in the air pump chamber. The air pump piston moves with the liquid pump piston between charge and discharge positions of the air pump piston in the air pump chamber. The air pump piston is also mounted to the liquid pump piston for limited relative movement between the two pistons that enable venting of the air pump chamber when the air pump piston is moved to its charge position relative to the air pump chamber. 
     The liquid pump chamber communicates with the continuous passage through both an inlet passage and an outlet passage. The inlet passage and the outlet passage are spaced from each other along the continuous passage of the sprayer housing. The air pump chamber also communicates with the continuous passage of the sprayer housing through an outlet passage that communicates with the continuous passage. 
     The single valve member is inserted into the continuous passage of the sprayer housing and is positioned in the continuous passage between the liquid pump chamber inlet passage and the liquid pump chamber outlet passage. The single valve member has a cylindrical base that seats in the continuous passage of the sprayer housing between the liquid pump chamber inlet passage and the liquid pump chamber outlet passage and divides the continuous passage of the sprayer housing into the liquid discharge passage on one side of the valve member base and the liquid supply passage on the other side of the valve member base. 
     A pair of coaxial resilient sleeves or tube valves project upwardly from the valve member base. A first, inner sleeve engages against the interior surface of the liquid discharge passage and controls the flow of liquid out of the liquid pump chamber outlet passage. Thus, the first resilient tube valve functions as the check valve in the liquid discharge passage that allows liquid flow from the liquid pump chamber to the liquid discharge passage, but prevents the reverse flow of liquid. 
     The second, inner sleeve engages against the interior surface of the discharge passage and controls the flow of air out of the air pump chamber outlet passage. Thus, the second resilient tube valve also functions as a check valve in the discharge passage that allows air flow from the air pump chamber to the discharge passage, but prevents the reverse flow. 
     A stem projects downwardly from the center of the valve base and a resilient disk valve is provided on the distal end of the stem. The length of the stem positions the disk valve below the liquid pump chamber inlet passage in the liquid supply passage. 
     A cylindrical valve seat insert is inserted into the liquid supply passage below the disk valve. The valve seat insert has an annular peripheral surface that seats against a portion of the disk valve adjacent its peripheral surface. An interior bore extends through the valve seat insert and defines a portion of the liquid supply passage. The dip tube is inserted into the valve seat interior bore at the bottom of the valve seat. Thus, the disk valve seating against the annular peripheral surface of the valve seat insert functions as the check valve that allows liquid flow through the dip tube and the liquid supply passage to the liquid pump chamber, but prevents the reverse flow of liquid. 
     A manual trigger is attached to the exterior of the sprayer housing and is operatively connected to the liquid pump piston and the air pump piston to cause the pistons to reciprocate through their respective pump chambers on manual manipulation of the trigger. The reciprocation of the liquid pump piston between charge and discharge positions of the liquid pump piston in the liquid pump chamber draws liquid through the dip tube and unseats the disk valve allowing the liquid to be drawn through the liquid supply passage and the liquid pump chamber inlet passage into the liquid pump chamber. Reciprocation of the liquid pump piston also forces the liquid from the liquid pump chamber through the liquid pump chamber outlet passage displacing the first resilient tube valve from its engagement with the interior surface of the liquid discharge passage and pumping the liquid through the discharge passage. The reciprocation of the air pump piston between charge and discharge positions of the air pump piston in the air pump chamber allows air to be drawn into the air pump chamber. As the liquid pump piston moves toward its charge position, the air pump piston moves to a limited extent relative to the liquid pump piston causing an air vent passage to open. As the air pump piston moves toward its charge position in the air pump chamber, air from the exterior environment of the trigger sprayer is drawn through the air passage and into the air pump chamber. When the liquid pump piston is moved toward its discharge position in the liquid pump chamber, the air pump piston again moves relative to the liquid pump piston in an opposite direction, closing the air vent passage. Continued movement of the air pump piston toward its discharge position in the air pump chamber forces the air from the air pump chamber through the air pump chamber outlet displacing the second tube valve from its engagement with the interior surface of the discharge passage and mixing the air under pressure with the liquid in the discharge passage producing a foam that is discharged through the discharge orifice of the sprayer nozzle assembly. 
     The construction of the air foaming trigger sprayer described above with the single valve element having both a disk valve to control the liquid drawn into the liquid pump chamber and a pair of tube valves to control the discharge of the liquid from the liquid pump chamber and air from the air pump chamber reduces the component parts of prior art trigger sprayers by providing a single valve member with three valve elements. The mounting of the air pump piston for limited movement relative to the liquid pump piston to open an air passage also eliminates the need for an additional air vent valve in the trigger sprayer construction. This further reduces the number of component parts of the trigger sprayer. The reduction in the number of component parts that go into the assembly of the trigger sprayer reduces its manufacturing costs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features of the invention are set forth in the following detailed description of the preferred embodiment of the invention and in the drawing figures wherein: 
         FIG. 1  is a front elevation view of the trigger sprayer of the invention; 
         FIG. 2  is a side sectioned view of the trigger sprayer of the invention along the line  2 - 2  of  FIG. 1 ; and, 
         FIG. 3  is a perspective view of the disassembled component parts of the trigger sprayer. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The air foaming trigger sprayer of the invention is similar in construction to the trigger sprayer disclosed in U.S. Pat. No. 6,641,003 B1, assigned to the assignee of the present invention and incorporated herein by reference. Because many of the component parts of the trigger sprayer disclosed in the above-referenced patent are employed in the construction of the trigger sprayer of the invention, these common component parts will first be generally described. 
       FIG. 3  shows the disassembled component parts of the trigger sprayer  12  that include the sprayer housing  14 , the trigger  16 , the discharge nozzle  18 , the sprayer shroud  22 , the liquid pump piston and vent piston assembly  24 , the valve member  26 , the valve seat insert  28  and the dip tube  32 . Each of the component parts is constructed of a resilient plastic material, as is typical. However, the material employed in constructing the valve member  26  is more resilient and flexible than that of the other component parts of the trigger sprayer. 
     Referring to  FIGS. 1 ,  2  and  3 , the sprayer housing  14  is connected to a separate liquid container (not shown) by a connector cap  34 . The connector cap  34  is a separate component part that is mounted on the sprayer housing  14  for rotation of the cap relative to the sprayer housing. However, the connector cap  34  could be an integral part of the sprayer housing  14  to reduce the number of separate component parts of the trigger sprayer. 
     The interior of the sprayer housing  14  is formed with a cylindrical vent chamber  36 , a cylindrical liquid pump chamber  38 , a liquid supply passage with a cylindrical interior surface  42  and a liquid discharge passage that is comprised of a first, vertical section with a cylindrical interior surface  46  and a second horizontal section  48 . The liquid supply passage  42  extends from an inlet opening in the sprayer housing to the liquid pump chamber  38  and the liquid discharge passage  46 ,  48  extends from the liquid pump chamber  38  to an outlet opening in the sprayer housing. A liquid spinner assembly  52  is provided at the outlet opening of the discharge passage second section  48 . The construction of the spinner assembly  52 , the discharge passage second section  48 , the liquid pump chamber  38  and the vent chamber  36  are similar to those of prior art trigger sprayers. 
     The continuous passage formed by the liquid supply passage  42  and the first section of the liquid discharge passage  46  communicates with the interior of the liquid pump chamber  38  through a liquid pump chamber inlet passage  56  and a liquid pump chamber outlet passage  58 . A portion of the passage  62  is positioned between the liquid pump chamber inlet passage  56  and the liquid pump chamber outlet passage  58 . The continuous passage also communicates with the interior of the vent chamber  36  through a vent passage  64 . The discharge passage first section  46  has a larger interior diameter portion  72  adjacent the liquid pump chamber outlet passage  58  and a smaller interior diameter portion  74  adjacent the discharge passage second section  48 . 
     The exterior surface of the sprayer housing  14  is provided with features that attach the shroud  22 . A pair of flanges  76  project downwardly from the opposite sides of the sprayer housing for mounting the trigger  16  to the sprayer housing. The housing has a cylindrical collar  78  that surrounds the outlet of the discharge passage  48 . The collar  78  receives the discharge nozzle  18 . 
     The piston assembly  24  is basically comprised of a liquid pump piston  82  that is mounted on a piston rod assembly  84 . A vent piston  88  is formed as part of the rod assembly  84 . The liquid pump piston  82  is mounted in the liquid pump chamber  38  for reciprocating movements between charge and discharge positions of the liquid pump piston relative to the liquid pump chamber. A coil spring  86  biases the liquid piston  82  toward the discharge position. The vent piston  88  is mounted in the vent chamber  36  for reciprocating movements between closed and opened positions of the vent piston  88  relative to the vent chamber  36 . The functioning of the liquid pump piston  82  to pump liquid through the sprayer housing  14  is known in the art and will not be explained in detail. Additionally, the functioning of the vent piston  88  to vent the interior of a container attached to the sprayer housing  14  is known in the art and will not be explained in detail. The piston assembly  24  is connected to the trigger  16  for reciprocating movement of the piston assembly in response to pivoting movement of the trigger. The piston assembly  24  is clipped to the trigger  16  so that the piston assembly is pushed into the pump and vent chambers  38 ,  36  and pulled out of the pump and vent chambers in response to the pivoting movement of the trigger  16  relative to the sprayer housing  14 . 
     The trigger  16  has a pair of pivot slots  92  at the top of the trigger. The slots  92  are assembled to the sprayer housing flanges  76  mounting the trigger  16  for pivoting movement on the housing  14 . 
     The discharge nozzle  18  is mounted on the sprayer housing collar  78  for rotation of the nozzle. The discharge nozzle  18  is provided with interior axial grooves that align with and come out of alignment with axial grooves provided on the spinner assembly  52 , as is known in the art. This enables the discharge nozzle  18  to be selectively moved between an “off” position and a “foam” position as is known in the prior art. 
     As stated earlier, the valve member  26  is constructed of a resilient plastic material that is slightly more flexible than the remaining component parts of the trigger sprayer  12 . Referring to  FIG. 1 , the valve member is constructed with a cylindrical base  94 . A first outlet valve element in the form of a resilient hollow tube or sleeve valve  96  projects outwardly from the valve base  94 . The tube valve  96  has an exterior surface diameter dimension that is slightly larger than the interior diameter dimension of the large interior diameter portion  72  of the discharge passage. A second outlet valve element in the form of a resilient hollow tube or sleeve valve  98  projects outwardly from the valve base  94 . The second sleeve valve  98  is concentric and contained inside the first sleeve valve  96 . The second sleeve valve  98  has an exterior surface diameter dimension that is slightly larger than the interior diameter dimension of the small interior diameter portion  74  of the discharge passage. A valve stem  102  projects outwardly from the base  94  of the valve member. An inlet valve element in the form of a disk valve  104  is provided on the distal end of the stem  102 . 
     The valve member  26  is assembled into the continuous passage of the sprayer housing  14  defined by the first section of the discharge passage  46  and the liquid supply passage  42 . The valve member is positioned in the sprayer housing as shown in  FIG. 2  with the valve member base  94  engaging against the annular interior surface  62  of the continuous passage. This positions the valve member base  94  between the liquid pump chamber inlet passage  56  and the liquid pump chamber outlet passage  58 . In this position the valve member base  94  separates and seals the liquid supply passage  42  from the liquid discharge passage first section  46 . In addition, the second sleeve valve  98  is positioned in the liquid passage second section  74  and engaging in sealing engagement with the small interior diameter portion  74  of the discharge passage. The stem  102  of the valve member positions the disk valve  104  in the supply passage  42  below the liquid pump chamber inlet passage  56 . 
     The valve seat insert  28  shown in  FIG. 5  has a cylindrical interior bore  106  that extends entirely through the insert. The dip tube  32  is inserted into the bore  106  at the bottom of the insert and the dip tube  32  and the insert interior bore  106  form a portion of the liquid supply passage leading to the liquid pump chamber inlet passage  56 . A center column  108  is positioned in the center of the valve seat insert interior bore  106 . A circular valve seating surface  112  extends around the valve seat bore  106 . The circular valve seating surface  112  rises slightly above the end of the center column  108  as can best be seen in  FIG. 2 . A cylindrical exterior surface of the valve seat insert  28  is provided with an outwardly projecting tab  114 . 
     As shown in  FIG. 2 , the valve seat insert  28  is assembled into the sprayer housing  14  by being inserted upwardly through the liquid supply passage  42  from the bottom of the sprayer housing. The insert  28  is inserted after the valve member  26  has been assembled into the sprayer housing  14 . The insert  28  is pushed upwardly through the liquid supply passage  42  until the projecting tab  114  on the insert exterior surface engages in the vent chamber opening in the vent passage  64 . This secures the valve seat insert  28  in the liquid supply passage  42 . In this position of the valve seat insert  28  the center column  108  of the insert engages against the center of the disk valve  104  and the circular seating surface  112  of the insert engages against a peripheral portion of the disk valve  104  and pushes the disk valve peripheral portion slightly upwardly as shown in  FIG. 2 . This provides a sealing engagement between the insert circular seating surface  112  and the peripheral portion of the disk valve  104 . 
     In addition to the vent chamber  36  and liquid pump chamber  38 , the trigger sprayer of the invention includes an air pump chamber  118  on the sprayer housing  14 . The air pump chamber  118  includes a cylindrical side wall  122  that extends outwardly from the sprayer housing  14 . The side wall  122  completely surrounds and contains the liquid pump chamber  38 . Thus, the air pump chamber  118  and liquid pump chamber  138  are coaxial. The air pump chamber side wall  122  extends outwardly from a cylindrical end wall  124  of the air pump chamber, to a circular distal end  126  of the side wall. An air pump outlet passage  128  passes through the pump chamber end wall  124  and communicates the interior volume of the air pump chamber  118  with the discharge passage  46 . 
     An air pump piston  132  is mounted in the air pump chamber  118  for reciprocating movements between charge and discharge positions of the air pump piston relative to the air pump chamber. The air pump piston  132  has a cylindrical exterior surface  134  that engages in a sealing, sliding contact with an interior surface of the air pump chamber side wall  122 . The air pump piston also has an annular end wall  134  and a cylindrical collar  136  that surrounds a center opening of the end wall. The piston collar  136  surrounds a cylindrical extension  138  of the piston rod assembly  184 . An interior diameter dimension of the air piston collar  136  is slightly larger than an exterior diameter dimension of the piston rod extension  138 , enabling the collar  136  and the air pump piston  132  to move slightly relative to the piston rod assembly  84 . An annular shoulder  142  projects radially outwardly from the piston rod extension  138 . A plurality of axially extending ribs  144  also extend radially outwardly from the piston rod extension  138 . There is an axial spacing between the piston rod extension shoulder  142  and the ribs  144  that is slightly larger than the axial length of the air piston collar  136 . This enables the air piston  132  to reciprocate axially on the piston rod extension  138  between the annular shoulder  142  and the ribs  144 . When the air pump piston  132  moves relative to the piston rod extension  138  and engages with the ribs  144  in the position shown in  FIG. 2 , an air flow passage is established between the interior surface of the air piston collar  136  and the exterior surface of the piston rod extension  138 . This enables the interior volume of the air pump chamber  118  to be vented to the exterior environment of the trigger sprayer  12 . When the air pump piston  132  moves in the opposite direction and the piston annular end wall  134  engages against the piston rod extension shoulder  142 , the air flow passage between the air piston collar  136  and the piston rod extension  138  is sealed closed. This prevents air flow between the exterior environment of the trigger sprayer  12  and the interior volume of the air pump chamber  118 . 
     In the operation of the trigger sprayer  12  when the liquid pump chamber  38  has not yet been primed with liquid and air fills the chamber, manually squeezing the trigger  16  toward the sprayer housing  14  compresses the air in the liquid pump chamber  38 . The compressed air is communicated through the liquid pump chamber outlet passage  58  to the exterior surface of the second sleeve valve  98 . This causes the second sleeve valve  98  to move away from its sealing engagement with the small interior diameter portion  74  of the discharge passage opening the discharge passage. The air from the liquid pump chamber is pumped through the discharge passage and is dispensed from the trigger sprayer through the discharge nozzle  18 . The pressure created in the liquid pump chamber  38  causes the peripheral portion of the disk valve  104  to seat against the circular seating surface  112  of the valve seat insert  28  preventing the compressed air from being pumped downward through the dip tube  32  and into the liquid container attached to the trigger sprayer. 
     Manually squeezing the trigger  16  also causes the piston rod extension  138  to move through the opening in the air piston collar  136  until the air piston annular end wall  134  seats against the piston rod shoulder  132 . This seals closed the air pump chamber  118  and causes the air pump piston  132  to move toward its discharge position in the air pump chamber. This compresses the air in the air pump chamber  118 . The compressed air in the air pump chamber  118  is communicated through the outlet passage  128  of the chamber to the exterior surface of the first sleeve valve  96 . This causes the first sleeve valve  96  to move away from its sealing engagement with the larger interior diameter portion  72  of the discharge passage, opening the discharge passage. The air from the air pump chamber  118  is pumped through the discharge passage and mixed with the air from the liquid pump chamber  38 . The air from both of these passages is dispensed from the trigger sprayer through the discharge nozzle  18 . 
     On manually releasing the trigger  16  the coil spring  86  pushes the trigger away from the sprayer housing  14 . This movement of the trigger pulls the liquid pump piston  82  outwardly through the liquid pump chamber  38  toward its charge position relative to the pump chamber. The removal of the air pressure on the exterior surface of the second sleeve valve  98  causes the resilient sleeve valve to move into sealing engagement with the small interior diameter portion  74  of the discharge passage. This creates a vacuum in the liquid pump chamber  38  that pulls the peripheral portion of the disk valve  104  out of engagement with the circular seating surface  112  of the valve seat insert  28  and draws liquid from the container up through the dip tube  32  and the liquid supply passage  42  into the interior of the liquid pump chamber  38 . 
     The movement of the piston rod assembly  84  toward the charge position of the liquid pump piston  82  by the coil spring  86  also causes the piston rod extension  138  to move to the left as viewed in  FIG. 2 . For a small portion of the movement of the piston rod extension  138 , the extension moves relative to the air piston collar  136  and the air pump piston  132 . This causes the piston rod extension annular shoulder  142  to disengage from its sealing engagement with the air piston annular end wall  134 . This again opens the vent path between the interior surface of the air piston collar  136  and the exterior surface of the piston rod extension  138 . The relative movement of the piston rod extension  138  continues until the ribs  144  on the extension engage the collar  136  of the air piston. Further movement of the piston rod extension  138  causes the air pump piston  132  to move in the air pump chamber  118  toward its charge position relative to the air pump chamber. This creates a vacuum in the air pump chamber  118  that draws air from the exterior environment through the air flow path established between the air piston collar  136  and the piston rod extension  138  into the air pump chamber. 
     By subsequent manual squeezing of the trigger  16  toward the sprayer housing  14  the liquid in the liquid pump chamber  38  is forced through the pump chamber outlet passage  58  displacing the second sleeve valve  98  from its sealing engagement with the small interior diameter portion  74  of the discharge passage and forcing the liquid through the discharge passage to be dispensed from the discharge nozzle  18 . The air pump piston rod extension  138  again moves relative to the air pump piston  132  causing the annular shoulder  142  of the rod extension to come into sealing contact with the annular end wall  134  of the air piston. This again seals closed the air flow path between the air piston collar  136  and the piston rod extension  138 . Further movement of the trigger causes the piston rod extension  138  to push the air pump piston  132  toward the discharge position of the air piston in the air pump chamber  118 . This compresses the air in the air pump chamber and forces the air through the air pump chamber outlet passage  128  displacing the first sleeve valve  96  from its sealing engagement with the large interior diameter portion  72  of the discharge passage. This causes the pressurized air to mix with the liquid flowing through the discharge passage, creating a foam that is dispensed from the discharge nozzle  18 . 
     The construction of the valve member  26  with a pair of sleeve valves  96 ,  98  and disk valve  104  on a single component part of the trigger sprayer  12 , and the construction of the coaxial liquid pump chamber  38  and air pump chamber  118  and the respective coaxial pistons  82 ,  132  enables the trigger sprayer  12  to be compactly constructed of a reduced number of separate component parts. The reduction in the total number of component parts needed to assemble the trigger sprayer reduces its manufacturing costs. 
     Although only one embodiment of the trigger sprayer of the invention has been described above, it should be understood that other modifications and variations could be made to the trigger sprayer without departing from the scope of the invention defined by the following claims.