Abstract:
A liquid pump for pumping groundwater samples from small diameter sub-terrain wells. The pump comprises a tubular casing having swaged ends and provided with inlet apertures on its side wall, a top cap and a bottom cap each provided with a bladder mandrel, a coil spring biasing the caps, a flexible bladder separating the interior of the pump into a liquid chamber and a gas chamber, and a pair of poppet valves preventing backflow of the pumped liquid. The pump is actuated by alternately pressurizing and de-pressurizing the actuating gas, preferably air, in the gas chamber causing the bladder to alternately contract and relax. The bladder is formed with reduced diameter ends that allows for an increased stroke volume of the pump. The pump is operated by a precision dual range controller, specifically adapted for “low flow” sampling.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to liquid pumping and collecting apparatuses, and more particularly to a system for pumping underground liquid, such as groundwater samples, from small diameter wells. It should be noted, however, that the invention is also applicable and adaptable in various other applications that will occur to one skilled in the art from the disclosure herein. 
     2. Description of the Prior Art 
     Recent increases in public concern for the environment have resulted in various government-imposed environmental regulations with regard to groundwater quality and land-site cleanup projects. Among such regulations are requirements relating to the monitoring and sampling of water quality of aquifers as sources of drinking water. In response to these requirements, water quality analytic capabilities have been improved and water-sampling equipment has been developed. However, presently most sampling using bladder pumps employs permanently installed dedicated pumps in monitoring wells. Current portable equipment for the groundwater sampling is relatively heavy, bulky, and thus difficult to transport from one monitoring site to another. 
     One of the preferred types of pumps for groundwater sampling or other pumping applications is a submersible, fluid-actuated pump wherein the actuating fluid is preferably a gas such as compressed air. A flexible bladder member in this type of pump separates and isolates the interior of the pump into two chambers: a liquid chamber that contains the sample fluid and is in communication with both the pump inlet and outlet, and a gas chamber surrounding the first chamber, and connected to a source of the actuating gas, with the bladder disposed therebetween. The pumped liquid is conveyed through the pump by alternately pressurizing and venting or relieving the pressure in the gas chamber to contract and relax the bladder member, thus alternately decreasing and increasing the volume of the liquid chamber. The pumped liquid is drawn into the liquid chamber during such increases in volume under the influence of the natural hydrostatic head of the groundwater or other pumped liquids and is discharged through the pump outlet during such decreases in volume, thereby conveying the pumped liquid through the pump. 
     The conventional bladder pumps employ ball-type check valves that control flow of liquid trough the pump. However, the ball-type check valves have proven to be not very efficient, especially in low-flow applications where the velocity with which water enters the pump intake is low. Ball members of the check valves are prone to roll around valve seats and, thus are slow to respond to the change of the water flow direction. 
     The need therefore exists for a liquid sampling bladder pump with more efficient check valves. 
     SUMMARY OF THE INVENTION 
     The present invention alleviates the drawbacks of the prior art. The present invention provides a pump for a wide variety of applications, including, but not limited to, groundwater quality applications, withdrawing and collecting contaminated groundwater or other subterranean liquids from a landfill-site having a plurality of in-ground wells. The novel pump may be built with a small outside diameter, such as ¾″ or ⅞″ and is adapted to sample temporarily and/or permanently installed small diameter monitoring wells. The bladder pump of the present invention is particularly effective for conducting “low-flow sampling” from monitoring wells where minimal purging is undertaken prior to sample collection. Please note that low-flow refers to the velocity with which water enters pump intake and that is imparted to the formation pore water in the immediate vicinity of the well screen. 
     The preferred liquid sampling pump is an air-operated, gas-displacement bladder pump having a generally hollow cylindrical body submersible in the in-ground well. The pump body includes a liquid inlet with an inlet cone-shaped check valve for allowing one-way fluid flow from the in-ground well into the housing interior, and a liquid outlet with a similar outlet cone-shaped check valve allowing one-way fluid flow from the pump body interior to the discharge collection equipment. The cone-shaped check valves provide better effectiveness than conventional ball-type check valves. 
     An exemplary control apparatus in some applications for supplying and controlling an operating fluid for a gas-displacement pump supplies pulses of a pressurized operating fluid, such as air, into the pump body interior in order to forcibly displace and discharge liquid material through the outlet. Between pressurized pulses of the operating fluid, the control apparatus relieves the pressure of the other operating fluid in the pump body interior in order to permit liquid material to flow, under the influence of its own hydrostatic head, into the pump housing through the inlet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in light of the accompanying drawings, wherein: 
     FIG. 1 is a fragmentary longitudinal sectional view of a liquid sampling system; 
     FIG. 2 is a perspective view of a controller apparatus of FIG. 1; 
     FIGS. 3 a  and  3   b  are fragmentary cross-sectional views of upper and lower portions, respectively, of a liquid pump in accordance with the first embodiment of the present invention; 
     FIG. 4 is a cross-sectional view of a push-fit fitting; 
     FIG. 5 is a fragmentary cross-sectional view of a cone-shaped check valve in accordance with the present invention; 
     FIGS. 6 a  and  6   b  are fragmentary cross-sectional views of upper and lower portions, respectively, of a liquid pump in accordance with the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 of the drawings illustrates an underground liquid sampling system indicated generally by reference numeral  1 . For purposes of illustration, the liquid sampling apparatus is shown as installed in a monitoring well  2 . A fluid sampling pump  10  is disposed within the well casing  4  of the monitoring well  2  and is submerged beneath the level of the groundwater  6  to a suitable depth for obtaining representative groundwater samples. 
     As is explained in further detail below, the liquid sampling pump  10  in accordance with the present invention, is a bladder-type fluid-actuated pump, wherein the actuating fluid is a pressurized gas, preferably compressed air, and includes a plurality of inlet openings  39  and an outlet fitting  14 . 
     A liquid conduit  16  is sealingly connected at one end to the pump outlet fitting  14  to provide direct sample delivery to a sample collection vessel  17 . A pressurized gas conduit  18  is connected at one end to a fluid fitting  20  of the pump  10 . The other end of the gas conduit  18  is selectively and removably connected to a precision dual range controller  100 . 
     Because the pump is preferably of a lightweight construction, the conduits themselves can frequently be used to hold and retain the pump in its submerged position in the well  2 . Preferably, the pump  10  is provided with an attachment device (not shown) that allows users to support the pump in the well with a covered steel cable. It will be appreciated that any other appropriate means for holding and retaining the pump  10  in its submerged position in the well  2 , commonly known to those skilled in the art, may be used. 
     The precision dual range controller  100  is selectively and removably connected to the pump  10  by means of the external gas conduit  18 . The preferred controller  100  is a portable, lightweight unit and includes means for alternately positively pressurizing and venting or relieving the pressure of the actuating gas in order to operate the liquid sampling pump  10 , as is explained below. 
     FIG. 2 illustrates a preferred physical arrangement for the dual range controller  100 , including a carrying case  102  for housing and transporting the portable controller apparatus from one monitoring site to another. The carrying case  102  generally includes an upper portion  104  hingedly connected to a base portion  106 , carrying handle (not shown), and upper and lower latches  110  and  112 . The carrying case  102  is preferably composed of high impact-resistant materials known to those skilled in the art for purposes of protecting the components of the controller  100 . The dual range controller generally includes two separate, switchable, pressure regulated air supply circuits, preferably 0-50 psi and 0-100 psi, each having a dedicated pressure gauge  122  and  123  respectively, a fitting  120  to which the external gas conduit may be connected, a pressure gauge  118  used to monitor the air supply provided to the controller  100 , and various controls. To enable precision control of the flow from the bladder pump, the controller  100  is provided with separate precision electronic timers to control the flow air to and from the pump  10 , each of which is adjustable in the range of 0.1 to 10 seconds. The carrying case  102  is especially adapted for ease and convenience of transportation of the controller and related components to monitoring sites to which access is limited or difficult. 
     The various individual components of the preferred controller apparatus  100  are well known to those skilled in the art and thus are described only schematically in terms of their functions. 
     As illustrated in FIGS. 3 a  and  3   b , the fluid sampling pump  10  in accordance with the first embodiment of present invention, includes a generally tubular pump casing  30  having a cylindrical wall  32 , a lower end  34  and an upper end  35 . The cylindrical wall  32  of the pump body  30  is swaged at the opposite lower and upper ends  34  and  35  thereof respectively. The lower end  34  of the pump body  30  is sealed with a bottom plug  38 . The upper end of the pump body  30  is closed with a top cap  40 . The casing  30  is swaged at its upper and lower ends to retain the bottom plug  38  and the top cap  40 . The top cap  40  is sealed to an internal surface of the wall  32  by means of O-rings  42  or other suitable sealing means known to those skilled in the art. 
     A bottom cap  60  is provided between the bottom plug  38  and the top cap  40 . The bottom cap  60  sealingly engages the wall  32  by means of O-rings  62 . The bottom cap  60  is provided with a communication passage  68  therethrough. The bottom cap includes an integrally formed bottom bladder mandrel  63 . However, a separate bottom bladder mandrel secured to the bottom cap by any appropriate means, is also within the scope of the present invention. 
     The interior of the pump body  30  is divided and isolated into two chambers by a generally cylindrical flexible bladder  50  having a central portion  51  and two opposite ends  52 . The bladder  50  defines a liquid chamber  55  in its interior and an annular fluid chamber  56  between an exterior of the bladder  50  and an interior wall surface of the pump body  30 . The bladder  50  is sealingly connected to a top bladder mandrel  70  at its upper end by means of O-rings  72  and a band clamp  74 , and to the bottom bladder mandrel  63  at its lower end by means of O-rings  64  and a band clamp  66 . The top bladder mandrel  70  is preferably threadedly attached to the top cap  40 . The top bladder mandrel  70  and the bottom bladder mandrel  63  are interconnected by a support member  54 . Preferably, the support member  54  is a solid rod. In this case, the top bladder mandrel  70  includes a number of apertures  79  providing the free flow of groundwater liquid between the liquid chamber  55  and the passage  75  in the bladder mandrel  70 , and the bottom mandrel  63  includes a number of apertures  69  providing the free flow of groundwater liquid between the liquid chamber  55  and the passage  68 . 
     However, the support member  54  may be in the form of a hollow tube provided with a number of apertures spaced at various locations along its longitudinal length in order to allow the free flow of groundwater fluid between the interior of the tube and the remainder of the liquid chamber  55 . In this case, no apertures  69  and  79  are formed in the mandrels  63  and  70  correspondingly. 
     A spring member, preferably a coil spring  36 , is disposed between the bottom plug  38  and the bottom cap  60  in order to bias the caps  40  and  60  toward the upper end of the pump casing  30 . 
     As illustrated in FIGS. 3 a  and  3   b , the bladder  50  is formed with the reduced diameter ends  52  relative to the central portion  51  thereof. This allows for an increased stroke volume and, therefore, increased efficiency of the pump operation. 
     The top cap  40  is provided with an outlet liquid port  44 , and a fluid communication port  46 . The outlet fitting  14  is affixed to the liquid outlet port  44 . The actuating gas fitting  20  is affixed to the fluid communication port  46 . The fittings  14  and  20  are identical and may be conventional threaded fittings or any other appropriate fittings well known in the prior art. Preferably, push-fit barb fittings, illustrated in FIG. 4, are employed. They include a bore  14 ′( 20 ′), an O-ring seal  14   2 ( 20   2 ) and two sets of barbs  14   3 ( 20   3 ) and  14   4 ( 20   4 ) for sealing and security. 
     In the preferred embodiment, the lower end  34  of the pump casing  30  is provided with a plurality of liquid inlet apertures  39  in the wall  32 , located substantially between the bottom plug  38  and a bottom cap  60 . Preferably, the inlet apertures  39  are located in close proximity to each other forming a limited sampling area. This allows the pump  10  to sample a narrow stratum of liquid in the monitoring well. A mesh screen filter  37 , preferably, of stainless steel, is disposed within the casing  30  adjacent to the apertures  39  for filtering out solids greater than a predetermined size. 
     Furthermore, the top bladder mandrel  70  includes a communication passage  75  therethrough. An outlet cone-shaped check valve  80  for preventing backflow of the pumped liquid through the passage  75  to the liquid chamber  55  from the outlet port  44  is provided in the top cap  40 . Thus, when the pumped liquid, such as groundwater, is flowing through the pump in the direction indicated by flow arrows  87 , the groundwater passes around the outlet cone-shaped check valve  80  and through the outlet port  44  and the outlet fitting  14 . Backflow in the direction opposite that indicated by flow arrows  87 , is substantially prevented by sealing engagement of the outlet cone-shaped check valve  80  with a corresponding valve seat on the bladder mandrel 
     Correspondingly, an inlet cone-shaped check valve  90  for preventing backflow of groundwater or other pumped liquid through the inlet passage  68  and the inlet apertures  39  from the liquid chamber  55  is provided in the bottom cap  60 . The inlet cone-shaped check valve  90 , illustrated in detail in FIG. 5, comprises a housing  91  sealingly secured in the passage  68  by means of O-ring  92 , and a cone  96  trapped between valve seat  94  and cone retainer  93 . The housing  91  is provided with a communication port  95  selectively blocked and opened by the cone  96 . 
     Thus, when the pumped liquid, such as groundwater, is flowing through the pump in the direction indicated by flow arrows  87  (shown in FIG. 3 b ), the groundwater passes around the cone  96  and the cone retainer  93  and through the passage  68  into the liquid chamber  55 . Backflow in the direction opposite that indicated by flow arrows  87  is substantially prevented by sealing engagement on the cone  96  with the corresponding valve seat  94 . 
     Referring to FIGS. 1,  3   a  and  3   b , the preferred fluid sampling pump  10  is actuated by means of actuating gas supplied to the fluid chamber  56  which is alternately and sequentially subjected to positive and negative or reduced pressures. The alternate pressurizing and depressurizing of the actuating gas in the gas chamber  56  causes the bladder  50  to alternately expand and contract, thus alternately and sequentially decreasing and increasing the volume of the liquid chamber  55 . During such increases in volume, the groundwater is drawn from the well  12  into the liquid chamber  55  through the inlet apertures  39  in the casing  30  and the passage  68  in the bottom cap  60 . During such decreases in such volume, the groundwater is forced out of the liquid chamber  55  through the passage  75  in the top bladder mandrel  70  and the outlet port  44  in the top cap  40  and is passed through the outlet fitting  14  and the groundwater conduit  16  to be collected in the sample collection vessel  17 . The cone-shaped check valves  80  and  90  prevent the water from being discharged through the inlet apertures or drawing in through the outlet port. 
     The capacity of the pump  10  may be changed in different versions of the pump by changing the diameter of the tubular pump casing  30 , thereby changing the amount of water drawn in and forced out during the alternate contractions and relaxations of the flexible bladder  50 . Preferably, the bladder pumps in accordance with the present invention, may be manufactured with the outside diameter ¾, ⅞ and 1″ depending on the particular application. Theoretically, increasing the length of the pump wall  32  and correspondingly increasing the length of the bladder  50  would also increase the stroke volume. However, the longer pumps are subject to hang up in the non-plumb monitoring wells. For this reason, the bladder pumps for well monitoring ought to be designed as short as possible. 
     It should be noted that the various components of the pump  10 , contacting the pumped liquid, are preferably composed of relatively lightweight and low-cost synthetic materials that will not be corroded when exposed to the groundwater and that will not otherwise affect the composition of the groundwater flowing through the pump. Examples of such materials include stainless steel, rigid polyvinyl chloride (PVC), DELRIN and polytetrafluoroethylene (PTFE) marketed under the DuPont Teflon® trademark. The flexible bladder is preferably composed of a flexible synthetic material that also will not corrode or affect the composition of groundwater flowing therethrough, such as Teflon®. The casing  30  of the pump is preferably made of stainless steel. One skilled in the art will readily recognize, however, that the various components of the fluid sampling apparatus may be composed of other suitable non-corrosive materials. 
     FIGS. 6 a  and  6   b  illustrates a liquid sampling pump  10 ′ in accordance with the second embodiment of the present invention. With the reference to FIGS. 6 a  and  6   b , the parts in common with FIGS. 3 a  and  3   b  are designated by the same reference numeral. The pump  10 ′ includes a generally tubular pump casing  30  having a cylindrical wall  32 , a lower end  34  and an upper end  35 . The cylindrical wall  32  of the pump casing  30  is swaged at the opposite end  34  and  35  thereof. The lower end of the pump body  30  is sealed with a bottom plug  38 . The upper end of the pump body  30  is closed with a top cap  140 . The top cap  140  is formed integrally with a top bladder mandrel  143  provided with a communication passage  145 . The casing  30  is swaged at its upper and lower ends to retain the bottom plug  38  and the top cap  140 . The top cap  140  is sealed to an internal surface of the wall  32  by means of O-rings  142  or other suitable sealing means known to those skilled in the art. 
     A bottom cap  160  is provided between the bottom plug  38  and the top cap  140 . The bottom cap  160  sealingly engages the wall  32  by means of O-rings  162 . The bottom cap  160  is provided with an inlet liquid communication passage  168  therethrough. The bottom cap  160  is formed integrally with a bottom bladder mandrel  163 . The top and bottom bladder mandrels  143  and  163  respectively are interconnected with a tubular support member  54 . 
     A spring member, preferably a coil spring  36 , is disposed between the bottom plug  38  and the bottom cap  160  in order to bias the caps  140  and  160  toward the upper end of the pump casing  30 . 
     Furthermore, the lower end  34  of the pump casing  30  is provided with a plurality of liquid inlet apertures  39  in the wall  32 , located substantially between the bottom plug  38  and the bottom cap  160 . A mesh screen filter  37  is disposed within the casing  30  adjacent to the apertures  39  for filtering out solids greater than a predetermined size. 
     The interior of the pump body  30  is divided and isolated into two chambers by a generally cylindrical flexible bladder  50  having a central portion  51  and two opposite ends  52 . The bladder  50  defines a liquid chamber  55  in its interior and an annular fluid chamber  56  between an exterior the bladder  50  and the interior wall surface of the pump body  30 . The bladder  50  is sealingly connected to the top cap  140  and the bottom cap  160  at its opposite ends by means of O-rings  147  and  164  and band clamps  148  and  166  respectively. The tubular support member  54  is disposed within the liquid chamber  55  and includes a number of apertures  53  spaced at various locations along its longitudinal length in order to allow the free flow of groundwater fluid between the interior of the support member  54  and the remainder of the liquid chamber  55 . 
     As illustrated in FIGS. 6 a  and  6   b , the bladder  50  is formed with the reduced diameter ends  52  relative to the central portion thereof. This allows for an increased stroke volume and, therefore, increased efficiency of the pump operation. 
     The top cap  140  is provided with an outlet liquid port  144 , and a fluid communication port  146 . The outlet fitting  14  is affixed to the outlet liquid port  44 . The actuating gas fitting  20  is affixed to the fluid communication port  146 . The fittings  14  and  20  are identical and may be conventional threaded fittings or any other appropriate fittings well known in the prior art. Preferably, push-fit barb fittings, described in detail above and illustrated in FIG. 4, are employed. 
     Moreover, the bottom cap  160  includes a cone-shaped check valve  90  for preventing backflow of groundwater or other pumped liquid through the inlet passage  168  and the inlet apertures  39  from the liquid chamber  55 . Similarly, the top cap  140  includes the cone-shaped check valve  90  for preventing backflow of groundwater or other pumped liquid from the outlet port  144  to the liquid chamber  55 . The cone-shaped check valve  90  is described in detail above and illustrated in FIG.  5 . The operation of the pump  10 ′ is similar to the operation of the pump  10  described in hereinabove. 
     Therefore, the novel arrangement of the liquid sampling bladder pump of the present invention as constructed in the above-described embodiments provides simplified field application and easy deployment in non-plumb wells, and allows for obtaining representative samples of groundwater or other liquids. 
     The foregoing description of the preferred embodiments of the present invention has been presented for the purpose of illustration in accordance with the provisions of the Patent Statutes. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment disclosed hereinabove was chosen in order to best illustrate the principles of the present invention and its practical application to thereby enable those of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated, as long as the principles described herein are followed. Thus, changes can be made in the above-described invention without departing from the intent and scope thereof. It is also intended that the scope of the present invention be defined by the claims appended thereto.