Patent Publication Number: US-2004055402-A1

Title: Probe holder

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates to holders for detecting probes. This invention also relates to a system and method for the accurate detection of a substance with a probe. In a more specific respect, this invention relates to a holder, system and method for accurate process material moisture content determinations with infra red and near infra red probes.  
       [0003] 2. Background and Discussion of the Prior Art  
       [0004] Infra red probes are used to detect moisture content in various production operations, such as in paper mill processing and wood drying. Infra red probe readings are often inaccurate in that moisture or contaminants collect on the detecting end of the probe thereby introducing errors in the moisture content reading.  
       [0005] In pharmaceutical process operations, it is important to accurately determine the moisture content of the process material in dryers and processing vessels for controlled drying or processing. Overdrying adversely impacts on crystal size in drying pharmaceutical crystals. Crystal size and shape is a factor in pharmaceutical properties, and accurate moisture content determination in crystal is therefore imperative. The present pharmaceutical process technique product moisture content determination entails use of sample collectors. In such process techniques, the operator periodically opens the process vessel and uses the sample collector to collect a sample from the product mass or slurry. The collector with sample is taken to a laboratory for moisture content analysis. The moisture content determination is then communicated to the process operator for process control adjustment or even shutdown. This technique is unduly time consuming, labor intensive, necessitates disruptive entry into the process vessel, and the moisture content determination is not in ongoing real processing time. Further, the sample removal from the otherwise closed process vessel in itself may introduce outside moisture or contaminants with consequential additional error in the moisture product content determination.  
       [0006] A direct, online, rapid and accurate means for moisture content determination of product in dryers and other process vessels is desired for pharmaceutical processing especially with the moisture content determination being effectively free of contaminant and non-product moisture induced error and process disruption.  
       SUMMARY OF THE INVENTION  
       [0007] A moisture detecting probe is mounted in a holder, which holder includes a gas distribution conduit to provide gas at a predetermined sufficiently high pressure across the detecting end of the probe to clear the probe of contaminants and moisture.  
       [0008] The detecting probe and holder combination of the present invention, in one preferred embodiment, is disposed in the wall of an enclosed process vessel or chamber to determine the moisture content of a product undergoing processing or drying. A near infra red probe is used to detect the moisture content. A controller is operably connected to the vessel so that at predetermined periodic intervals just prior to each desired moisture content determination, a high pressure pulse of gas, such as air or nitrogen, is provided to the holder conduits and transversely across the detecting end face of the near infra red probe. The high pressure pulsed gas assuredly clears the probe detecting end of residual moisture and/or particulates. The controller then immediately actuates the probe for a real time accurate moisture content reading.  
       [0009] The gas may be initially provided by a supply controller at a constant low pressure purge of no more than about 10 psi, and immediately prior to the probe reading, the controller is actuated to supply the gas at a higher pressure of 10 to 45 psi or more to assuredly clear the probe detecting end. The high pressure gas purge is terminated. A master controller actuates the probe immediately after the high pressure gas purge is terminated. The low pressure gas purge is then reinstituted until just prior to the next desired predetermined probe reading.  
       [0010] In a more specific preferred embodiment, the present invention includes one or more of the foregoing inventive features in operable combination with a pharmaceutical process vessel or dryer for an accurate real time determination of the moisture content of the pharmaceutical process material or product undergoing processing or drying. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is a perspective exploded view of the probe holder and probe;  
     [0012]FIG. 2 is a sectional view of the probe holder taken along line  2 - 2  of FIG. 1, with the probe disposed in the holder;  
     [0013]FIG. 3 is a proximate end view of the coupler portion of the probe holder;  
     [0014]FIG. 4 is a proximate end perspective partial sectional view of the probe holder; and  
     [0015]FIG. 5 is a schematic block diagram of the system and method of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0016] The terms “near infra red” and “NIR” as used hereinbefore and hereinafter throughout the specification and claims refer to wavelengths of between about 1100 and 2200 nm.  
     [0017] Referring to the FIGS., there is shown probe holder  10  and near infra red probe  11 . Probe holder  10  is, in general terms, an integral assembly constructed of distally disposed tubular member or coupler  12 , annular flange or manifold  13 , and proximately disposed tubular lock member  14 . Holder  10  slidably receives probe  11  in central orifice  15 . Holder  10  is generally constructed of machined metal components, namely, coupler  12 , flange  13  and lock member  14  which are slidably inter-fitted and welded in an integral construction.  
     [0018] Coupler  12  has a distally disposed annular end face  16 , cylindrical outer wall  17  with distally disposed annular groove  18 , a proximately disposed annular end wall  19 , a first inner cylindrical wall  20  terminating in end wall  21 , a second inner cylindrical wall  22  which forms a portion of central orifice  15 , and a distally disposed cylindrical wall  92 . End wall or lip  23  is disposed between and contiguous with walls  22  and  92 . End wall  23  functions as an abutment or seat for the distal end  71  of probe  11 . Probe  11 , when seated against end wall  23 , is in fluid tight disposition in holder  10  by means of a deformable swagelock (not shown) of well known construction disposed between probe  11  and holder central orifice  15 . An O-ring (not shown) can also be provided to insure the fluid tight seal of the probe in the holder. Other fluid tight mechanical sealing means known in the art may likewise be used to securely hold probe  11  in holder central orifice  15 .  
     [0019] A series of three spaced holes  25  (typical) are drilled in holder  10 . Holes  25  are circumferentially disposed at  120 _, and equally radially disposed with respect to central orifice axis  26 . Holes  25  extend from coupler proximately disposed wall  19  to coupler distally disposed end face  16 . A distal end weld plug  27  (typical) forms a blind hole for each respective hole  25 . A series of three cross-holes  28  (typical) are drilled in holder  10 . Cross-holes  28  are circumferentially disposed and extend from outer cylindrical surface  17  to inner cylindrical wall  92 . Each cross-hole  28  intersects and communicates with a respective hole  25 . Cross-hole  28  terminates in a respective end opening  30  in wall  92 . Each cross-hole  28  has a radially disposed central axis  31  which is perpendicularly disposed to and intersects central orifice axis  26 . A plug weld  32  (typical) forms a blind hole for each cross-hole  28 . In this manner of construction, holes  25  are contiguous with respective cross-holes  28  to form respective channels or conduits for the simultaneous distribution of a gas in a radially inward direction through end openings  30 , for purposes hereinafter appearing.  
     [0020] Coupler proximately disposed annular end wall  19  is formed with an annular semi-circular groove  39  which is contiguous with the distal end opening  35  (typical) of each respective hole  25 . Flange  13  is formed with a distal wall  36 , proximately radially inwardly disposed wall  37  and contiguous outwardly disposed wall  108 . Contiguous walls  37  and  108  provide a frustoconical configuration which is cojoined to distal wall  36  by peripheral cylindrical wall  109  (FIG. 4). An annular semi-circular groove  40  is formed in flange distal wall  36  which is similarly sized to groove  39  so that when wall  36  abuts wall  19 , complimentary grooves  39  and  40  form annular channel or orifice  42 . An angularly disposed hole  43  is drilled in flange  13  to receive gas supply hose  44 . Hose  44  has an inlet  45  and outlet  46 . Hose outlet  46  is disposed within flange  13  and is contiguous with annular channel  42  and one of the coupler holes  25 . Hose  44  is welded to flange  13  at circular mating corner  74 . In this manner of construction, gas enters hose inlet  45 , passes through hose  44  and outlet  46  into annular orifice  42 , and then simultaneously distributed through each hole  25  to each cross-hole  28  and in turn to each respective end opening  30 .  
     [0021] Lock member  14  Is formed with a distally extending cylindrical portion  48  having an outer surface or wall  49 , transversely disposed distal end wall  50  and an inner cylindrical wall  51 . Lock member end wall  50  abuts coupler end wall  21 . Lock member inner cylindrical wall  51  is flush with coupler inner cylindrical wall  22  to form the full length of central orifice  15 . A weld (not shown) is made at inner joining line  65  to provide an integral coupler and lock member construction (FIG. 4).  
     [0022] Flange  13  is formed with inner cylindrical wall  54  which is sized to slidably receive lock member outer wall  49 . With flange  13  disposed between lock member  14  and cojoined to coupler  12 , flange distal wall  36  abuts coupler wall  19 , and flange proximate wall  37  abuts lock member wall  57 . Lock member  14  is formed with proximate hexagonal outer peripheral portion  58 , cylindrical portion  59 , and hexagonal portion  60 . Flange  13  is fixedly seated between lock member hexagonal portion  60  and coupler proximate end wall  19 . Welds (not shown) are provided respectively at hexagonal mating line  78  and circular mating line  79  to provide an integral coupler, flange and lock member construction.  
     [0023] Coupler circumferential groove  18  and flange annular groove  98  are sized to receive respective O-rings  81  for fluid tight engagement within vessel wall mount or collar  82  of process vessel or chamber  85  (FIG. 2). Other fluid tight sealing means well known in the art are also within the contemplation of the invention.  
     [0024] Referring specifically to FIGS. 2 and 5, the enclosed vessel or chamber  85  has an integral collar  82  which is formed with sleeve  96  into which holder  10  with probe  11  are slidably received, forming assembly  100 . Assembly  100  is in fluid tight construction with respect to chamber  85  by means here-before described or by other vessel fluid tight constructions well known in the art. Gas supply controller  88  supplies gas to assembly  100  through hose  44  and holder  10 , and in turn across the detecting end face of probe  11 . A process instrument  86  is operably disposed with respect to vessel  85 , so that at a predetermined process parameter or condition such as each rotation of process slurry mixer blade, a signal is transmited to master controller  87 . Master controller  87  upon receipt of the signal actuates gas supply controller  88  to supply pressurized gas at a predetermined pressure to holder  10  to clear the probe detecting end face as hereinbefore described. Master controller  87  then immediately, after clearance of the probe detecting end face, signals probe controller  89  to take a probe reading. Probe  11  transmits the reading to probe controller  89  and in turn to a reader or recorder  90 . An operator or automatic process controller (not shown) can then adjust the process parameters or shut down the process in accordance with the particular probe reading.  
     [0025] In a preferred embodiment, probe  11  is a near infra red (NIR) probe that detects the moisture content of the process material (not shown) in closed process vessel  85 . A slurry mixer blade (not shown) rotates in the slurry (e.g. pharmaceutical product crystals) undergoing processing (e.g. drying). Master controller  87  actuates a low pressure gas (e.g. nitrogen) purge of about 5 to 10 psi across the end face of probe  11 . Process instrument  86  detects each rotation of the slurry blade as it passes the probe  11 , and accordingly signals master control  87  to actuate gas supply  88  to provide a surge or blast of high pressure gas at 10 to 45 psi or more across the sapphire crystal end face of the NIR probe to assuredly clear the probe distal end face. Master controller  87  then stops the high pressure gas surge momentarily and simultaneously actuates a probe moisture content reading via probe controller  89 . The moisture content reading is transmitted to reader or recorder  90 . The master controller  87  then actuates a low psi gas purge of about 5 to 10 psi, and repeats the probe reading cycle. In this manner, the invention provides an intra-vessel product moisture content determination which is free of error introduced by moisture and/or contaminants, and further provides a real time accurate moisture content determination without operator interface, undesired process disruption or process vessel opening. The process operator merely reads the reader and determines whether to adjust the process parameters or stop the process.  
     [0026] While the preferred embodiment is to provide low pressure and high pressure gas pulses, it is to be understood that other variations of gas pulses are within the contemplation of the invention. By way of example, it has been found that the low pressure pulse may be terminated when the product crystals slurry nascent liquid is greatly diminished as when the pharmaceutical crystals drying approaches the desired end point.  
     [0027] The present invention is particularly useful in, but not limited to, the formation and drying of crystals in the manufacture of pharmaceuticals. Insofar as overdrying adversely impacts crystal size, close monitoring of the moisture content of the crystals slurry is important. The afore-described preferred embodiment is particularly useful in such applications. It is however within the broad contemplation of the invention to use the probe holder in diverse environments, including by way of example, process vessels, reactors and dryers. The probe holder is preferably used in a closed vessel or chamber but may also be used in processing environments which communicate with the ambient air. Continuous as well as batch process operations are within the contemplation of the present invention.  
     [0028] The probe is preferably a near infra red probe of Hasteloy construction having flexible fiber optics which provide NIR through a detecting sapphire window end face onto the product undergoing moisture content determination. One preferred commercially available probe system useful in the present invention is the XDS NIR SmartProbe Analyzer manufactured by Foss, Silver Spring, Md.  20904 . While the preferred embodiment is described with respect to an NIR probe and to a pharmaceutical product moisture content determination, it is within the contemplation of the invention to use the probe holder with other probes, by way of example, infra red probes and other types of substance or condition detecting probes having a detecting end face. The invention contemplates using any gas which is non-reactive with respect to the particular product and process. Useful gases are air, nitrogen, the inert gases (e.g. argon), and the like.  
     [0029] It is also within the contemplation of the present invention to provide fully automated cooperation between the probe readings and the process controllers, wherein by way of example, the process operations parameters would be automatically adjusted concomitantly with each periodic moisture content determination.  
     [0030] While the foregoing describes a preferred embodiment of the invention, it is within the ordinary skill of the practitioner to make obvious modifications and changes within the broad contemplation of the invention as set forth in the adjoined claims