Abstract:
An improved bailer which allows for the variance of flow into the bailer through use of attachments with varying inflow orifice sizes. As the size of the orifice changes, the weight of the apparatus can also be changed allowing for an only slightly negative buoyancy of the apparatus. The attachment may also be designed to include features for filtering unwanted particulates from the sample.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Applicant&#39;s invention relates to apparatuses for retrieving liquid samples from reservoirs of liquid. 
   2. Background Information 
   Groundwater pollution is an ever-growing concern in today&#39;s environments, and the need for groundwater monitoring is increasing, especially around chemical storage facilities, land fills, military bases, airports, and underground storage tanks. 
   The typical groundwater monitoring program consists of a series of monitoring wells located at different points around the margin of an aquifer, in close and distant proximities from the potential contamination source. Each monitoring well consists of a well casing which lines the well bore, the hole extending from the ground surface to the groundwater. 
   At least until very recently, most monitoring samples have been taken through the use of devices known as bailers. A bailer is an elongated, slender tube which is sized to pass through the well casing of a test well. The insertion end of an advanced bailer includes a one-way valve which allows water to flow into the bailer as it is lowered into the well casing, but hinders effluent flow as the bailer is lifted from the water. 
   Bailers have been in widespread use in the groundwater sampling process because they are inexpensive to purchase, inexpensive to fabricate, portable, simple to operate, and require no external power source. However, inherent in the presently-known bailer designs, is the inability to control the flow rate of the sample—a serious problem in light of relatively new knowledge concerning factors affecting the quality of samples taken in test wells. 
   It has been determined that if the extraction rate exceeds the recharge rate, the sample may be compromised through various means, including the increase of the turbidity of the sample, the mixing of stagnant and fresh water in the well, and the disturbance and re-suspension of settled solids. The results of the sample analysis then may be skewed, showing either higher or lower levels of contamination in the groundwater then actually exist, depending on the characteristics of the contaminant. As a result, Federal and state governments now require that samples of ground water be extracted at a rate not exceeding the recharge rate of the sampling well. Resulting guidance documents now state that bailers are ill-suited for low flow. Thus, use of conventional bailers for test well sampling is very nearly obsolete. 
   The preferred method for test well sampling now involves the use of pumps. Ironically, although the pump flow rates are easily controlled, the problems associated with using pumps at test well sites are the very reasons that most samplers changed from using pumps to using bailers in the past. Pumps are expensive, harder to clean and operate, and require an external power source. Pumps also have go through general maintenance procedures to maintain the life of the pumps, increasing the cost. 
   In view of the foregoing, it would well serve those involved in test well monitoring to provide some means by which test well sample may be taken with the simplicity and economy of bailers, yet still comply with the new low-flow sampling requirements. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an improved bailer to allow for low flow sampling as is desirable to obtain quality samples from ground water test wells and, in some cases, required by the governmental regulations, in any event to provide an alternative to presently available, and much more expensive alternatives for obtaining such samples. 
   In satisfaction of these and related objectives, Applicant&#39;s present invention provides a bailer of an improved design which allows for the variance of flow into the bailer through use of attachments with varying inflow orifice sizes. As the size of the orifice changes, the weight of the apparatus can also be changed allowing for an only slightly negative buoyancy of the apparatus. The attachment may also be designed to include features for filtering unwanted particulates from the sample. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevational side view of the Applicant&#39;s improved bailer with low-flow attachment engaged. 
       FIG. 2  is an elevations side view of the Applicant&#39;s low-flow attachment incorporating the filtering device. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , the bailer of Applicant&#39;s invention is identified by the reference numeral  10 . The preferred embodiment of bailer  10  includes a cylindrical, plastic tube  12 . 
   The bailer has an insertion or distal end  14  and a proximal end  16 . The preferred embodiment of Applicant&#39;s bailer  10  includes a distal terminus cap  18  and a proximal terminus cap  20 , and a negative buoyancy device  23  and housing  24 . Proximal terminus cap  20  includes a generally dome-shaped portion  24  from which extends a nesting lip  22 . 
   Nesting lip  22  extends from the margin of the dome portion  24  of cap  20  to generally define a cylindrical structure which snugly nests within the lumen of plastic tube  12 . To insure that proximal terminus cap  20  does not accidentally disengage from plastic tube  12 , the two should be suitably bonded together (such as through use of sonic welding) during assembly of bailer  10  through means appropriate for the material from which bailer  10  is fabricated (polyethylene in the case of Applicant&#39;s current preferred embodiment). 
   The preferred embodiment of proximal terminus cap  20  has two attachment orifices  26  passing through the dome-shaped portion  24 . Attachment orifices  26  provide the means by which bailer  10  is attached to cording (not shown in the drawings) by which bailer  10  will be lowered into and removed from a well. 
   A terminal segment of cording will be passed through a first orifice  26  from the convex side of dome-shaped portion  24 , and then passed through the other orifice  26  from the concave side of dome-shaped portion  24 . In order to insure that bailer  10  assumes as near a vertical orientation as possible as it is suspended from a cord during sample taking, orifices  26  should reside as mirror images of each other on either side of a bisecting line which divides equally the dome-shaped portion  24  of terminus cap  20 . For the same reason, the axis of symmetry of dome-shaped portion  24  should, when terminus cap  20  is installed on plastic tube  12 , correspond to the longitudinal axis of symmetry of plastic tube  12 . 
   The configuration of proximal terminus cap  20  as just described virtually eliminates the possibility of a bailer  10  becoming lodged against some irregularity in the well casing surface. Unlike the angular margins of presently available bailers, the purely rounded surfaces of Applicant&#39;s bailer  10  will simply slide past all obstructions in the well casing, except those which would have prevented initial insertion of bailer  10  in the first place. 
   The preferred embodiment of the negative buoyancy device  23  is a series of masses, in which the weight of the apparatus can be changed by removing or adding mass. The weight of the apparatus is used to aid in the control of the flow rate into the apparatus. The negative buoyancy device is enclosed in housing  25 , which keeps the weights separate from the sample, thereby avoiding contamination. The preferred embodiment of the housing  25  is a cylindrical casing that should be permanently bonded to the bailer and is made of an inert material, to avoid contamination. 
   Distal terminus cap  18  also includes a generally dome-shaped portion  28  from which extends a nesting lip  30 . Nesting lip  30  is configured substantially identically to nesting lip  22  of proximal terminus cap  20  and is attached in the same manner. 
   The preferred embodiment of distal terminus cap  18  exhibits an intake orifice  32 , a flow control insert  31 , and a flow control orifice  33 , through which water passes when gathering a test sample. The orifice  32  is, in the preferred embodiment surrounded by an annular flange  34  which serve to prevent interference with operation of the ball valve  36  by objects which may contact the distal end  14  of bailer  10 . The flow control insert  31 , in the preferred embodiment is compression fit to the intake orifice  32  to shut off flow around the insert and direct the flow through the flow control orifice  33 . The flow control orifice  33 , in the preferred embodiment is centered on the inserted end of the flow control insert. The flow control orifice size varies and combined with the amount of weight in the negative buoyancy device  23  can control the fill rate of the apparatus ranging from less than 100 milliliters per minute to over 1 liter per minute. 
   The flow control insert  31  may also be covered with a particulate filtering device  40  as shown in  FIG. 2 . The filtering device  40  covers the in-take end of the flow control insert  31 . It is used to prevent clogs occurring in the flow control orifice. The preferred embodiment of the filtering device is a stainless steel mesh screen that is placed over the protruding end of the flow control insert. 
   As with proximal terminus cap  20 , distal terminus cap  18  is configured whereby the axis of symmetry of dome-shaped portion  28  should, when terminus cap  18  is installed on plastic tube  12 , correspond to the longitudinal axis of symmetry of plastic tube  12 . The orifice  32  is, in turn, centered on the same axis of symmetry of plastic tube  12 . This configuration insures that orifice  32  (and flange  34 ) is directed parallel with the path of bailer  10  and is less likely to scrap sediment, etc. from the casing wall as the bailer  10  is lowered for sample gathering, and thereby risk contamination of the sample. 
   While the greater concern which is addressed by the rounding of margins for bailer  10  is that of avoiding juxtaposition of a proximal, angular margin with a casing surface irregularity after the bailer is inserted into a well casing, the rounding of the distal end  14  surfaces of bailer  10  also has significant utility. 
   Certain irregularities in well casings are not so profound as to risk trapping the bailer  10  in the well casing. Nevertheless, some irregularities may be pronounced enough such that an angular margin on the distal end of a bailer will abut the irregularity and thereby suspend the bailer above the level intended for sample taking. 
   Additionally, the engagement of a sharp edge with a well casing wall as the bailer is lowered may dislodge sediments and other accumulations on the well casing surface which may lead to local contamination of the underlying water supply to an extent which may render the sample unrepresentative of the actual over-all state of the water supply. In certain cases, this could lead to a “false positive” for serious levels of contaminants in a water supply, with potentially very costly and disquieting results. If, for example, a well test revealed an abnormal level of, perhaps, a heavy metal which had accumulated on the casing wall over time, but which was not at dangerous levels in the actual water supply, environmental regulations might, in the case of a producing water well, dictate suspension of operation of the subject well, and in other cases lead to costly investigations of nearby candidates for sources of pollution. 
   Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.