Abstract:
The present invention relates to a low profile, fine mist, finger-operated, precompression-type spray pump, and more particularly to a spray pump provided with a second valve of the novel structure being moveable between a poppet valve and a bottom entrance of housing, to precompress the fluid as a liquid content and then spray, whereby the spray pump can be operated even with a short travel distance of a piston, which enables to make the height of a push button spaced from a closure to be shorter than the existing ones, and the pumping process can be smoothly performed without leakage and can also be started with small empty pumping numbers. In addition, the spray pump according to the present invention is constructed with small numbers of constituent parts, resulting in the significant reduction of manufacturing cost and assembly cost.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a low profile, fine mist, finger-operated, precompression-type spray pump, and more particularly to a spray pump provided with a second valve having a novel structure being moveable between a poppet valve and a bottom entrance of a housing, to precompress a liquid to be sprayed, whereby the spray pump can be operated even with a short travel distance of a piston, which enables the height of a push button spaced from a closure to be shorter than in existing spray pumps, and the pumping process to be smoothly performed without causing dripping of the liquid at a nozzle and to be initiated with a small number of pumping actions under the condition that the housing is empty (“empty pumping number”). In addition, the spray pump according to the present invention is constructed with a small number of constituent parts, resulting in the significant reduction of its manufacturing cost and assembly cost. 
   Spray pumps which nebulize a liquid sealed in a container, that is, dispense it in the form of very small droplets through a nozzle in response to a user&#39;s pressing a push button provided at the upper part of a pump, are widely used due to many merits thereof. These pumps have been developed to have various configurations depending upon the characteristics of the liquid to be nebulized. (e.g., the viscosity of fluid), the amount of liquid to be pumped, etc. 
   Generally, the spray pumps nebulizing a liquid of low viscosity comprise: a closure holding the pump securely to the neck of a container, a housing guiding the flow of fluid, said housing being engaged to the closure and having a smaller diameter at its lower portion than at its upper portion; a piston being moveable coaxially within the housing, said piston having formed therein a vertical duct penetrating vertically; a poppet valve closing and opening the vertical duct of the piston by a rod, said rod being formed at the upper portion of the poppet valve; a spring providing an upward returning force to the piston or poppet valve; and a push button being mounted on the upper portion of the piston, said push button being provided with a nozzle at its lateral portion which communicates with the vertical duct. 
   Accordingly, when the push button is pressed so as to spray the fluid (i.e., a downward force is applied to the push button), the fluid present in the housing is pressurized to rise along the vertical duct and then spray through the nozzle. On the other hand, when the downward force having been applied to the push button is released, the vertical duct is closed by the rod of the poppet valve, and the inner pressure of housing drops while the piston moves upward, whereby the fluid present in the container enters the housing to compensate the reduced pressure thereof. 
   Various configurations of spray pumps have been developed whereby the pumping of fluid can be carried out by closing and opening the bottom entrance of a housing (hereafter, sometimes referred to as “a housing bottom entrance”) to vary the pressure in the interior of the housing (hereinafter, sometimes referred to as the “housing interior”). As a closing/opening means of the housing bottom entrance during pumping, a metal ball is generally used. However, the metal ball fails to entirely close the housing bottom entrance because of its spherical shape. Furthermore, the metal ball cannot rapidly respond to the variation of pressure of the housing&#39;s interior, resulting in leakage by dripping at the nozzle, characterized by the leakage of some fluid owing to a small gap between the metal ball and the housing bottom entrance and hence the slow loss of pressure from the housing&#39;s interior. In addition, the metal ball acts to close the housing bottom entrance by gravity upon application of a downward force to the push button, and open it in response to loss of pressure in the housing&#39;s interior upon release of the downward force; however, the density of fluid present in the housing&#39;s interior increases upon application of the downward force to the push button and thus the relative gravity of the metal ball decreases, making the rapid closing of housing bottom entrance difficult. Therefore, owing to the pressure loss in the housing&#39;s interior and the slow response to the variation of pressure, a leakage by dripping occurs at the initial step and final step of a spraying procedure. 
   In order to solve these problems, spray pumps of various configurations have been developed which can precompress the fluid present in a housing during pumping. In such precompression-type spray pumps, the point of contact between a rod of a poppet valve and a vertical duct of a piston opens for a short time to enable spraying, only when the pressure of the fluid present in the housing&#39;s interior reaches a certain level, namely, the threshold pressure, upon application of a downward force to the push button, and then rapidly closes after completion of the spraying. 
   Examples of such precompression-type spray pumps include a spray pump disclosed in U.S. Pat. No. 5,277,559 in which a sliding seal is hold moveable on a poppet valve, a spray pump disclosed in Korean patent application No. 2002-67623 to the present applicant, in which two springs are provided, a spray pump disclosed in Korean registered utility model No. 204024 to the present applicant, in which two metal balls are provided, and a spray pump disclosed in U.S. Pat. No. 5,096,097 in which a second cylinder extends upwardly from a housing bottom entrance. These spray pumps have some technical merits, respectively, but also have demerits as described herein below. 
   The spray pump in U.S. Pat. No. 5,277,558 has a demerit that the sliding seal being moveable along the outer surface of a poppet valve must be molded with high precision, or else will malfunction. The spray pump in Korean patent application No. 2002-67623 and the spray pump in Korean registered utility model No. 204024 exhibit an excellent precompression function but have demerits of relatively high manufacturing cost due to the use of numerous parts. The spray pump in U.S. Pat. No. 5,096,097 has a demerit that a housing of relatively large size is required to provide the variable volume sufficient for compression of the fluid with the housing&#39;s interior, thereby needing a piston able to travel a large distance. 
   In recent, there has been a great demand for a spray pump which exhibits a high performance and also, when mounted on a container, does not render a final product unattractive. When a spray pump is mounted on a container, portions exposed outside are a push button and a closure. A large-sized push button or closure are likely to be perceived as unattractive on a final product and hence, from this viewpoint, a button and closure of small size are required. Meanwhile, the variable volume of a housing&#39;s interior and the travel distance of a piston must be sufficiently large to attain the desired pumped volume of fluid. The variable volume of a housing&#39;s interior is determined by the length and width of the housing and, considering the whole dimension of a pump to be mounted on a container, there is a certain it to the length and width of the housing. Where the lengths and widths of housings are the same in two spray pumps, the volume of fluid pumped depends upon the travel distance of the piston. When it is required to make the travel distance of piston to be long, the length of button or closure, more specifically, the height of button spaced from the closure, must be large, thereby remarkably degrading the appearance of a final product as stated above. Accordingly, a spray pump is required which operates based on a short travel distance of the piston, and ultimately a short height of the button spaced from the closure. 
   In addition, it is desirable that the number of pumping actions to be performed to effect a first spraying under the condition that the housing&#39;s interior is empty (“empty pumping number”), be minimized to in convenience of use, especially in the case of certain pharmaceutical products which should not be held for a long time in the housing&#39;s interior. 
   SUMMARY OF THE INVENTION 
   The purpose of the present invention is therefore to eliminate the drawbacks of the prior arts and to satisfy the requirements mentioned above. 
   More specifically, the object of the invention is to provide a spray pump which can operate even with a short travel distance of a piston, allowing the height of a button spaced from a closure to be small, and which enables the pumping procedure to be performed smoothly without causing leakage by dripping at the nozzle, and which can be constructed with a small number of constituent parts, thereby significantly reducing its manufacturing cost and assembly cost, and which can also start spraying with a low empty pumping number. 
   In order to attain this object, the low profile, fine mist, finger-operated, precompression-type spray pump according to the present invention comprises:
         a closure holding a pump securely to the neck of a container;   a housing guiding the flow of a liquid to be sprayed, said housing being constructed as a multi-step structure, with the diameter thereof reducing downwardly;   a piston being moveable in both upward and downward directions within the housing, said piston being provided with a vertical duct penetrating therethrough;   a poppet valve closing and opening the vertical duct of piston by a rod, said poppet valve being provided with the rod at the upper portion thereof and a cylindrical part extending from the lower portion thereof;   a spring providing an upward returning force to the poppet valve;   a push button being engaged to the top of the piston, said push button being provided with a nozzle at its lateral portion which communicates with the vertical duct; and   a second valve closing a housing bottom entrance with a glans part in compression mode and opening it in release mode, said second valve being disposed between the poppet valve and the housing bottom entrance, in which said second valve is provided with a cylindrical body being moveable coaxially within the cylindrical extending part of the poppet valve and the glans part has a larger diameter than the cylindrical body part, said glans part being positioned at the lower portion of the cylindrical body.       

   “Compression mode” in the present invention means an operating state wherein, by applying a downward force to the push button, the housing bottom entrance is closed and the piston moves downward and, more specifically, includes a “precompression mode” wherein the housing bottom entrance is closed by the glans part of the second valve and the fluid present in the housing&#39;s interior is compressed, and a “spray mode” wherein, when the pressure of fluid in the housing&#39;s interior reaches a certain level, namely, the threshold pressure, the vertical duct is opened and thus the fluid present in the housing&#39;s interior is sprayed through a nozzle. 
   “Release mode” in the present invention means an operating state wherein, by releasing the downward force having been applied to the push button, the housing bottom entrance is opened from the glans part of the second valve and, more specifically, includes an “inflow mode” wherein while the piston moves upward by the upward returning force of the spring, the fluid present in the container is introduced into the housing&#39;s interior through the housing bottom entrance, and a “rest mode” wherein the piston is positioned at the apex of its stroke and thus no longer moves upward. Therefore, the pumping procedure of the spray pump according to the present invention is performed with one cycle of “rest mode→precompression mode→spray mode→inflow mode.” 
   In the spray pump of the present invention, the second valve acts to close and open the housing bottom entrance with its glans part in the pumping procedure, allowing the fluid to be introduced into the housing&#39;s interior and the introduced fluid to be precompressed and then sprayed. More specifically, while the upper portion of second valve, i.e., the cylindrical body, is in moveable contact with the cylindrical extending part of the poppet valve such that the outer surface of cylindrical body slides upward and downward along the inner surface of cylindrical extending part, the lower portion of second valve, i.e., the glans part, closes and opens the housing bottom entrance. 
   Since the second valve is made of plastic material, like the housing, when the glans of the second valve comes into contact with the housing bottom entrance, the contact sealing effect is excellent, allowing almost no pressure loss in the housing&#39;s interior during the pumping procedure, compared to using a metal ball as an opening-closing means as in the prior art, which contributes to the prevention of leakage by dripping. Moreover, in the compression mode, as the poppet valve moves downward, the cylindrical body of the poppet valve being in contact with the cylindrical extending part of the poppet valve is also dragged downward, thereby the housing bottom entrance being immediately closed by the glans part of the second valve. In the release mode, as the poppet valve returns upward by an upward returning force of the spring, the housing bottom entrance is immediately opened in the same manner. Accordingly, when the pump is operated, the response speed of the glans part for closing and opening the housing bottom entrance is very fast. Due to this feature, the spray pump according to the present invention can have a relatively larger, variable volume in the same housing interior as that used in the prior art, thus pumping can be performed even with a short travel distance of the piston, which makes it possible to shorten the height of the push button spaced from the closure, and also reduce the empty pumping number. 
   In a preferable embodiment of the present invention, the top of the housing bottom entrance is formed to be concave in shape, and the bottom of the glans part of the second valve is formed to be convex in shape, enabling them to come into close contact with each other. Accordingly, when the second valve descends to close the housing bottom entrance in the pumping procedure, the convex portion of the glans part perfectly occludes the concave portion of the housing bottom entrance, thereby exhibiting a high sealing effect. 
   In another preferable embodiment of the present invention, a plurality of teeth are circumferentially formed on the outer surface of glans part of the second valve, and a plurality of grooves corresponding to the teeth are circumferentially formed on the inner surface of the housing in proximity to the housing bottom entrance, and when the teeth are engaged to the grooves, a plurality of through passages are created between them. Accordingly, the upward and downward movement of the second valve can be stably performed by the integration of these teeth and grooves, resulting in a smoother pumping action. 
   In another preferable embodiment of the present invention, an annular protuberance is formed on the outer surface of cylindrical body of the second valve and/or the inner surface of cylindrical extending part of the poppet valve at a position where the cylindrical body is in moveable contact with the cylindrical extending part, resulting in a further improved sealing effect 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  shows a longitudinal section view of the spray pump according to an embodiment of the present invention being in rest mode; 
       FIG. 1B  shows a longitudinal section view of the spray pump of  FIG. 1A  being in spray mode; 
       FIG. 2  shows in enlarged scale a longitudinal section view of a part of the spray pump of  FIG. 1A , showing operation of some constituent parts being in spray mode; 
       FIG. 3  shows in enlarged scale a longitudinal section view of a part of the spray pump of FIG. A, showing operation of some constituent parts being in inflow mode; 
       FIG. 4  shows a top view (a), a longitudinal section view (b), and a bottom view (c) of a housing used in the spray pump according to an embodiment of the present invention; 
       FIG. 5  shows a top view (a) and a longitudinal section view (b) of a poppet valve used in the spray pump according to an embodiment of the present invention; 
       FIG. 6  shows a top view (a) and a longitudinal section view (b) of a second valve used in the spray pump according to an embodiment of the present invention. 
   

   DESIGNATION OF THE REFERENCE NUMERALS 
   
       
         100 : spray pump 
         200 : closure 
         300 : housing 
         400 : piston 
         500 : poppet valve 
         600 : spring 
         700 : push button 
         800 : second valve 
     
  
   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   As shown below, the description refers to the relevant drawings in order to describe the present invention more clearly, and such description is not to be interpreted as limiting the present invention in any way. 
     FIG. 1A  shows the longitudinal section view of a spray pump according to one embodiment of the present invention being in the release mode (more particularly, rest mode), and  FIG. 1B  shows the longitudinal section view of the spray pump being in the compression mode (more particularly, spray mode). 
   Referring to  FIG. 1A , a spray pump  100  comprises, a closure  200  for securely holding the pump  100  to the neck of a container (not shown); a housing  300  for guiding the flow of the fluid to be sprayed, and which is configured as a multi-step structure; a piston  400  being moveable upwardly and downwardly along the inner surface of the housing  300 , and which has a vertical duct  410  formed along the central axis thereof; a poppet valve  500  for closing and opening the vertical duct  410  with a rod  510 , which has the rod  510  as an upper portion thereof and a cylindrical extending part  520  as a lower portion thereof; a spring  600  for providing an upward returning force to the poppet valve  500 ; a push button  700  engaged to the top of the piston  400  and having a nozzle  710 , formed at its later side, being in communication with the vertical duct  410 ; and a second valve  800  for closing and opening a bottom entrance  310  of the housing  300  with a glans part  820 , and which is disposed between the poppet valve  500  and the housing bottom entrance  310 . 
   A cylindrical sleeve  210  of a closure  200  is screwed by a thread  212  formed thereon to the threaded neck of a container. A lateral part  220  horizontally extending from the sleeve  210  is resiliently bent such that it is held fast to the top of the housing  300  while being in sliding contact with the piston  400 . Such structural characteristics of the lateral part  220  are described in the PCT international patent application No. WO 02/33258 to the present applicant, which is incorporated into the present invention as a reference. 
   A housing  300  is configured as a multi-step structure with its diameter decreasing downwardly by steps. In the bottom entrance  310  of the housing  300  is inserted a suction tube (not shown), which is immersed in the fluid to be nebulized. The housing  300  is illustrated in more detail, referring to  FIG. 4  showing a top view (a), a vertical cross-sectional view (b) and a bottom view (c) thereof. In the housing  300  of the multi-step structure, a first step  320  is formed, as shown in  FIG. 1B , at the position where a piston  400  no longer moves downward in the compression mode, and a second step  330  is formed, as shown in  FIGS. 1A and 1B , at the position where a spring  600  is located, and a third step  340  is formed at the position where the second valve  800  closes and opens the housing bottom entrance  310  with the glans part  320  thereof. 
   As can be seen in the top view (a) of  FIG. 4 , the second step  330  is formed with a plurality of grooves  332 . The bottom of the spring  600  abuts against the top of these grooves  332 . The glans part  820  of the second valve  800  is also disposed at the second step  330 . As will be described later, when teeth  822  of the glans part  820  ( FIG. 6 ) are engaged to the grooves  332  of the second step  330 , a plurality of through passages are created between the teeth  822  and grooves  332 , through which the fluid present in a container is introduced into the housing&#39;s interior (S) in the inflow mode. The dimensions of the through passage are not particularly limited but, in consideration of rheological properties such as the viscosity of fluid, the volume of fluid to be pumped, etc., such dimensions can be determined by controlling the size, number and spacing of the grooves  332  and the teeth  822 . 
   Again referring to  FIG. 1A , the piston  400  is moveable upwardly and downwardly along the inner surface of the housing  300  under the sealing condition. The bottom of the vertical duct  410 , with which the rod  510  of the poppet valve  500  are in contact, is configured to have a narrow width to provide a high sealing effect in the precompression mode. 
   The poppet valve  500  is illustrated referring to  FIG. 5 , showing a top view (a) and a vertical cross-sectional view (b) thereof, and is moveable upwardly and downwardly together with the piston  400  in all the operation modes except the spray mode. Referring to the vertical cross-sectional view (b) of  FIG. 5 , the poppet valve  500  comprises the rod  510  of the upper portion, a supporting part  530  of the middle portion, and the cylindrical extending part  520  of the lower portion. As stated previously, the rod  510  acts to close and open the bottom of the vertical duct  410  of the piston  400 . For easy closing, the top of the rod  510  is preferably conical in shape. The supporting part  520  has a larger diameter than the rod and the cylindrical extending part  520 , and the top of the spring  600  abuts against the lower portion of the supporting part  520 . The side of the supporting part  520 , as shown in  FIG. 5A , is symmetrically cut such that the spaced distance thereof from the inner surface of housing  300  becomes larger to allow the fluid to rise more smoothly. The cylindrical extending part  520  is formed such that the cylindrical body  810  of the second valve  800  moves upwardly and downwardly along the inner surface thereof. For ensuring resilient contact with the cylindrical body  810 , an annular protuberance  522  protrudes inwardly at the bottom of the cylindrical extending part  520 . In another embodiment, the annular protuberance may be formed outwardly at the top of the cylindrical body  810 , or the annular protuberances may be formed both inwardly at the bottom of the cylindrical extending part  520  and outwardly at the top of the cylindrical body  810 , respectively. 
   Again referring to  FIG. 1A , the spring  600  is positioned between the second step  330  of the housing  300  and the poppet valve  500 , providing an upward returning force to the poppet valve  500  via the supporting part  530 . 
   The second valve  800 , disposed between the poppet valve  500  and the housing bottom entrance  310 , is illustrated referring to  FIG. 6  showing a top view (a) and a vertical cross-sectional view (b) thereof. Referring to the vertical cross-sectional view (b) of  FIG. 6 , the second valve  800  comprises the cylindrical body  810  of the upper portion and the glans part  820  of the lower portion, the glans part  820  having a larger diameter than the cylindrical body  810 . The cylindrical body  810  is moveable upwardly and downwardly along the inner surface of the cylindrical extending part  520  of the poppet valve  500 . In order for the body  810  to smoothly move within the extending part  520  while retaining the sealing condition, the outer diameter of the body  810  is formed to be slightly smaller than the inner diameter of the extending part  520  and simultaneously slightly larger than the inner diameter of the annular protuberance  522 . Since the extending part  520  is of resilient plastic material, the sealed state can be maintained between the extending part  520  and body  810  in the pumping procedure, and also the upward and downward movement thereof can be smoothly carried out. Moreover, a pair of small lugs  812  is formed on the outer surface of the body  810  in proximity to the glans part  820 . As will be illustrated later concerning the operation of pump  100 , when the poppet valve  500  descends and thus the fluid present in the housing&#39;s interior (A) is precompressed and sprayed in the compression mode, the cylindrical extending part  520  of the poppet valve  500  reaches the small lugs  812  of the second valve  800  at the time of completion of spraying and passes them in the continuous descent thereof, whereby the cylindrical extending part  520  is slightly separated from the body  812 , and then the pressurized fluid present in the housing&#39;s interior (S) is discharged though the separating gap toward the container. The detailed description of this procedure will be illustrated later with reference to the operation of the pump  100 . 
   Meanwhile, on the side surface of the glans part  820 , a plurality of teeth  822  are circumferentially formed. The teeth  822 , as stated previously, are engaged to the inner portion of housing  300  next to the housing bottom entrance  310 , i.e., to the grooves  322  of the second step  330  of the housing  300 . Accordingly, the upward and downward movement of the second valve  800  can be further stabilized by the coaxially-moveable engagement of the teeth  822  and grooves  332 . Furthermore, the bottom  824  of the glans part  820  is formed to be convex in shape, and the top  312  of the housing bottom entrance  310  corresponding thereto is concave. Therefore, when the glans part  820  closes the housing bottom entrance  310 , the sealing effect can be improved by the close contact between the two bodies. 
   Referring to  FIGS. 1A ,  1 B,  2  and  3 , the operation of the spray pump  100  according to the present invention is described hereafter.  FIGS. 1A and 1B  show the spray pump  100  in the rest mode and the spray mode, respectively. 
   In the rest mode of  FIG. 1A , as no external force is applied to the push button  700  of the pump  100 , the rod  510  of the poppet valve  500  closes the vertical duct  410  of the piston  400  by an upward returning force of the spring  600 . The glans part  820  of the second valve  800  is separated from the housing bottom entrance  310  to open the housing bottom entrance  310 . In some cases, the glans part  820  may close the housing bottom entrance  310  by the weight of the fluid present in the housing&#39;s interior (S). 
   As a downward force is applied to the pump  100  being in the rest mode by pressing the push button  700 , the piston  400  and poppet valve  500  are actuated, with the vertical duct  410  being closed by the rod  510 . At this time, the housing bottom entrance  310  is immediately closed by the descending glans part  310 , because the second valve  800 , of which the cylindrical body  810  is in contact with the cylindrical extending part  520  of the poppet valve  500 , descends together with the poppet valve  500  due to its frictional contact with the poppet valve  500 . As such, the spray pump  100  according to the present invention exhibits a rapid response to the application of external force in the compression mode. As the housing bottom entrance  310  is closed by the glans part  820 , the housing&#39;s interior (S) is wholly sealed. As the piston  400  continues to descend under this sealing condition, the cylindrical extending part  520  of the poppet valve  500  moves downward, with its inner surface being in contact with the outer surface of the body  810  of the second valve  800 , whereby the fluid present in the housing&#39;s interior (S) is pressurized. By this pressurization, the fluid can be precompressed until reaching a certain level, namely the threshold pressure, prior to spraying, thus the spraying procedure can be performed at a moment of reaching the threshold pressure, without leakage by dripping. 
   Accordingly, by continuous precompression, when the pressure of the fluid present in the housing&#39;s interior (S) reaches the extent of being able to overcome the compression force of the spring  600 , as mentioned above, spraying occurs as shown in  FIG. 1B . The working conditions of some constituent parts of the pump  100  being in the spray mode are illustrated in more detail in  FIG. 2 . Referring to  FIG. 2 , the rod  510  is separated from the bottom entrance  412  of the vertical duct  410 , and the pressurized fluid rises toward the vertical duct  410  through the generated gap. This spraying procedure occurs in an instant, and the pressure of the housing&#39;s interior (S) drops rapidly below the threshold pressure for spraying because of the discharge of the fluid toward the vertical duct  410 , whereby the vertical duct  410 , more specifically, the bottom entrance thereof, is again closed by the rod  510 . 
   Even after spraying, the distal portion  420  of the piston  400  continues to descend until reaching a first step  320  of the housing  300 , with the vertical duct  410  being closed by the rod  510 . As a consequence, the residual fluid remaining in the housing&#39;s interior (S) is again pressurized but the pressure is not increased sufficiently to cause another discharge of spray. This residual pressure is not preferred when the fluid present in the container is introduced into the housing&#39;s interior (S) in the following release mode, which will be illustrated later in more detail. 
   As the downward force having been applied to the push button  200  is released, the poppet valve  500 , as shown in  FIG. 3 , moves upward by an upward returning force of the spring  600 . Since the body  810  of the second valve  800  is in frictional contact with the extending part  520  of the poppet valve  500 , the second valve  800  also rises together with the poppet valve  500  by the frictional contact therebetween, whereby the housing bottom entrance  310  is opened immediately after the poppet valve  500  starts to move upward. When the glans part  820  of the second valve  800 , more particularly, the teeth  822 , reaches the bottom of spring  600 , the second valve  800  no longer moves upward and only the poppet valve  500  rises. Since the poppet valve  500  rises with its extending part  520  being in sealing contact with the body  810  of the second valve  800 , the volume of the housing&#39;s interior (S) increases, whereby the fluid present in the container is introduced into the housing&#39;s interior (S) through a through passage  332  between a second step  330  and the glans part  820  so as to compensate the reduced pressure in the housing&#39;s interior (S) (as shown schematically by the flow lines in  FIG. 3 ). 
   As stated previously, the residual pressure in the housing&#39;s interior (S), having been generated after spraying in the compression mode, remarkably reduces the driving force for the inflow of fluid into the housing&#39;s interior (S). Meanwhile, bubbles remaining in the housing&#39;s interior (S) after spraying are accumulated by continuous pumping, causing an air cushion phenomenon. Accordingly, it is desirable to reduce the pressure of the housing&#39;s interior (S) and remove the bubbles by discharging the fluid toward the container after spraying. In the spray pump  100  according to the present invention, since a pair of small lugs  812  are formed on the outer surface of the body  810  of the second valve  800  at the height where the annular protuberance  522  of the extending part  520  of the poppet valve  500  is positioned immediately after spraying, as shown in  FIG. 6B , the annular protuberance  522  passes over the small lugs  812  as the extending part  520  descends, as shown in  FIG. 2 , whereby the fluid present in the housing&#39;s interior (S) is discharged toward the container through the gap generated between the lugs  812 . For convenience of illustration,  FIG. 2  is depicted so that the flow of the fluid for upward spraying (as shown schematically by the large flow line) and the flow of the fluid for downward discharging (as shown schematically by the small flow lines) occur simultaneously; however, the height of positioning the small lugs  812  on the outer surface of the body  810  is preferably adjusted such that the downward discharging occurs immediately after completion of the upward spraying. 
   Again referring to  FIG. 3 , the inflow of fluid into the housing&#39;s interior (S) in the release mode is performed immediately after the piston  400  begins to rise. To the contrary, in the spray pump of U.S. Pat. No. 5,096,097 wherein a second cylinder extends upwardly from the housing bottom entrance, the inflow of fluid into the housing&#39;s interior can start only when an extending part of a poppet valve separates from the top of a second cylinder by the continuous rising of a piston. Therefore, in the spray pump of this type, where a considerable pressure remains in a housing&#39;s interior, for example, the complete spraying has been not accomplished, it is difficult for the fluid to be introduced into the housing&#39;s interior, unless a sufficient variable volume is guaranteed in the housing&#39;s interior. To ensure the sufficient variable volume, the spray pump of this type requires a long upward and downward travel distance of the piston if the height and width of housing is limited, which necessitates a great height of a push button spaced from a closure. Compared to this existing spray pump, the spray pump according to the present invention can provide a relatively large variable volume in the housing&#39;s interior, even with a short travel distance of the piston in the case of the same spraying amount, due to the rapid response of the variable volume upon application or release of the external force. Such rapid response also contributes to the reduction of the empty pumping number. 
   INDUSTRIAL APPLICABILITY 
   As described above, the low profile, fine mist finger-operated, precompression-type spray pump according to the present invention can be operated even with a short travel distance of its piston, thus it is possible to reduce the height of a push button spaced from a closure, which contributes to the beauty of a final product containing liquid to be sprayed, on which the spray pump is mounted. The spray pump according to the present invention can be smoothly pumped without leakage and also fabricated with a small number of constituent parts, resulting in the remarkable reduction of its manufacturing cost and assembly cost. In addition, it can start to pump with a small empty pumping number. 
   As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.