Abstract:
An instrument housing for a drill string, comprising: a cylindrical housing having a cavity for receiving an instrument assembly such as a transmitter sonde; an elongated side load opening disposed parallel with and toward one end of the cavity and formed through a side of the cylindrical housing into the cavity. The side load opening is substantially shorter than the length of the instrument assembly; and an elongated side load door assembly is configured to fit within the side load opening, to enclose and secure the instrument assembly within the cylindrical housing such that the instrument is protected from loss or damage due to loss or damage to the side load door during operation.

Description:
The present application claims priority in U.S. Provisional Patent Application Ser. No. 60/709,347 filed Aug. 18, 2005 and entitled “Sonde Housing.” 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present application relates to drilling apparatus for directional drilling in utility installations and, more particularly, to housings for drill string instrumentation such as sonde transmitters and the like. 
     2. Background Description of the Prior Art 
     Horizontal Directional Drilling (HDD) is a means of boring horizontally underground to provide utility installations and remediation of utility installations already in place. While most open areas are “open trenched” with various trenching equipment, the HDD boring rigs are used to “drill” a bore path under obstacles such as rivers, roads, railroads, other existing utilities etc. 
     An HDD drill rig consist basically of a boring machine and a drill string including drill pipe, locating electronics (aka transmitter, sonde or transmitter beacon, typically configured as an instrument assembly for being enclosed or packaged within a tubular housing), and a boring bit attached to the front of the drill string. A bore path is plotted and laid out for the contractors. The drilling crew then drills at an angle into the ground along the bore path until the desired depth is reached. The bore is then leveled out and advanced under the obstacle. During this time the locating electronics instrumentation is installed between the drill bit and the drill pipe for transmitting the drill bit&#39;s depth, pitch and clock location (e.g., at 12, 3, 6, or 9 o&#39;clock) to the surface. Once the desired bore length is reached under and past the obstacle, the bit is steered toward the surface. The pilot tool is then removed and a reamer can be used to open the hole to a larger diameter while pulling the drill pipe back. If the pilot hole is the desired size, the tool is removed and the pipe, conduit or “product” is pulled back through the hole. During drilling, the drill pipe is fed into the bore 10 to 15 feet at a time. Attached to the front of the drill pipe just behind the drill bit (or, alternatively, a mud motor) is the instrumentation package such as a sonde housing which houses and protects the sonde (transmitter). 
     With respect to the instrumentation package, currently there are two types of prior art sonde housing designs on the market. The first type of prior art housing is known as an “end load” sonde housing. The sonde is loaded from one end of the housing and secured therewithin. With no “door” or “lid” access to the sonde this design requires “breaking” the connection between housing and drill stem to obtain access to the sonde within the housing. However, this design allows for a full set of “water ports” to be machined within the wall space surrounding the sonde cavity allowing a large volume of drilling fluids to be pumped through the drill pipe and tool. The volume and pressure capacity of this design allow drillers to drive hydro/mechanical drilling tools in the hole often called “mud motors” 
     The “end load” design is preferred for its flow capabilities and the security it offers for the electronics in the sonde. Secured inside the end load housing, the sonde is rarely lost during the coarse of boring. However, since the transmitter is powered by batteries, the process of disconnecting the drill string from the housing and removing the sonde can be cumbersome and difficult. This is especially true on shorter, smaller diameter “in &amp; out” bores where the tool usually remains on the drill pipe from bore to bore. 
     The second type of prior art housing is known as a “side load” housing. It is more popular for use with smaller machines without the large pump capacity for mud motor drilling. These rigs use a variety of bits that drill by rotational force from the drill rig transferred through the drill pipe. The side load design allows easy access to the sonde for maintenance, battery changes and replacement of the sonde. On a side load housing the sonde is installed through an opening in the side of the housing that is long enough for the sonde to be inserted laterally, with its axis parallel to the axis of the sonde housing. The sonde is inserted parallel with the housing and secured in place. A housing door or “lid” is then attached to the housing to cover and protect the transmitter. 
     The side load feature is a time saving design but reduces the number of water ports that may be provided to direct fluid from one end of the housing to the other. This fluid restriction is the primary reason this housing design is not used with the larger machines. 
     Another drawback to the side load design is that, on occasion during the drilling process, due to deterioration or extreme rotational torque, the side lids or doors become dislodged from the housing. Once the door is dislodged from a closed position or removed the sonde is completely exposed and typically protrudes from the housing or even falls out of the housing. At that point the sonde is usually irretrievable or damaged beyond repair. The cost associated with this failure is usually the loss of the sonde ($2,000-$5,000) plus the added expense of “tripping” out of the hole, making repairs” and tripping back into the bore. 
     What is needed is an instrument housing for a drill string that provides full protection for the instrumentation, allows full capacity water ports for use with mud motors, provides for ease of assembly into a drill string, and provides an easily adjusted clocking mechanism for the instrument package, and is low in cost of manufacture. 
     SUMMARY OF THE INVENTION 
     Accordingly, an instrument housing for a drill string is described herein, comprising: a cylindrical housing having a centered axial bore forming a cavity for receiving an instrument assembly such as a transmitter sonde, the dimensions of the cross section of the cavity exceeding the diameter of the instrument assembly by a predetermined clearance; an elongated side load opening disposed parallel with the longitudinal axis of the cavity, formed through a side of the cylindrical housing and into the cavity opening, the side load opening having a length substantially less than the length of the instrument assembly; and an elongated side load door assembly, having first and second ends and configured to fit within the side load opening, for enclosing and securing the instrument assembly within the cylindrical housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side view of one embodiment of a sonde housing according to the present invention, having a sonde partially installed therewithin; 
         FIG. 2  illustrates an exploded side view of the embodiment of  FIG. 1  including a clocking mechanism, a spacer assembly, and a side load door in position for assembly, and further having the sonde in place within the cavity of the sonde housing; 
         FIG. 3  illustrates a side view of the embodiment of  FIGS. 1 and 2  following assembly; 
         FIG. 4  illustrates a cross section view of one embodiment of the sonde housing of  FIG. 3 ; and 
         FIG. 5  illustrates a cross section view of an alternate embodiment of the sonde housing of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Disclosed herein and illustrated in  FIGS. 1 to 4  is one embodiment of a new side load housing for and instrument assembly called a transmitter sonde, sometimes referred to as a ‘beacon.’ While the specific embodiment describe herein is a sonde housing according to the present invention, the principles of the invention are applicable generally to cylindrical instrument housings having round or rectangular cross sections, that enclose a generally tubular instrumentation assembly, and that are typically used in harsh environments. 
     The sonde housing of the present invention illustrated in the appended figures provides a side-loaded sonde housing that is more resistant to damage to the side loading door assembly, and to the transmitter sonde (or, simply, sonde) itself, that may result from the torque applied to the drill string during drilling. The novel sonde housing design not only reduces the possibility of door loss but also protects and secures the sonde in the event the door does fail. As will be described, the clocking mechanism for use with the sonde is simplified, to reduce the time required to load and calibrate the sonde within the housing. This design also allows for an increased number (3 or 4 or 5) of water ports to accommodate the water flow capacity requirements of mud motors, as compared with prior art side load designs. In the description that follows, the reference numbers identifying the various structural features remain the same throughout the five figures when they refer to the same structures. 
     Referring to  FIG. 1 , the side load sonde housing  10  of the present invention is made from either a tubular product or a solid material with a center bore or cavity  14  disposed along the longitudinal axis of the housing. The center cavity  14  may have a round cross section, or the cross section may be rectangular having interior wall surfaces  16  as in the illustrate embodiment shown in  FIGS. 4 and 5 . In other embodiments the cross section may have other shapes. The housing is typically fabricated from a heat treated and hardened 4140 or 4340 alloy of stainless steel. Around the center cavity  14  of the housing  10  in the body  12  (see  FIG. 4  or  5 ) of the housing  10 , several water ports  110  may be drilled the length of the housing  10 . The size and number of these ports  110  is determined by the drill rig and pipe size and the type of tools being used. Typically there are at least 3 or 4 such water ports  110 , although in conventional side load sonde housings having a full length side load door, the number of such side ports is limited to one or two such ports. 
     The center cavity  16  may be “plugged” and welded to provide a seal on each end  18 ,  20 . A side load door opening  30  is machined through the body  12  of the housing  10 . The door opening  30 , which is shorter than conventional side load sonde housings, and disposed near one end of the cavity, is approximately 60% to 80% of the length of the sonde  40 . Also machined in the body  12  of the sonde housing  10  are a series of narrow antenna ports  22  that permit the transmitted signal from the sonde or beacon  40  to be radiated from the sonde  40 . There are typically five such ports (two are shown in  FIG. 1 ), including one cut through the door  80 , shown in a longitudinal cross section. In some embodiments, the antenna ports  22  are cut using a circular saw blade and produce an antenna port cross section as shown by the arcuate lines  96  in  FIG. 2 . Further,  FIG. 1  illustrates a drilled, tapped, and countersunk hole called a “flush port”  24  for receiving a ¾ inch flush plug. The flush plug may be removed for cleaning the sonde housing  10  after use to remove mud, debris and other materials that accumulate in the housing  10  during drilling operations. At each end of the sonde housing  10 , the housing is machined to be coupled with other drill string components at the tapered and threaded tool joints  26 ,  28 . 
     Continuing with  FIG. 1 , the interior notches  34 ,  36  are machined in each narrow end of the opening  30  to allow the tabs  86 ,  88  machined on the door  80  to engage the housing  10 . An interior ledge  32  is also machined around the perimeter of the opening  30  to support the door  80  and to eliminate any deflection of the door  80  into the cavity  14  by forces occurring in the drill string path. The body  12  of the housing  10  further includes a drilled and tapped hole  54  for a third bolt  94  to secure the door  80  to the body of the housing  10 . A drilled and tapped hole  54  is also formed in the floor of the cavity in the housing to receive a second bolt  70  for securing the spacer  66  to the housing. The third bolt  94  and the second bolt  70 , as well as a first bolt  64  to be described may each preferably be, for example, a nylon pelleted, socket head shoulder bolt. 
     To install the sonde  40  into the housing  10 , the first end  42  of the sonde  40  is configured to be inserted into the center cavity  14  at an angle  50  relative to the longitudinal axis of the housing  10 . Before insertion, the sonde  40  may be oriented rotationally, so that, in the position illustrated in  FIGS. 1 ,  2 , and  3 , the keyway or slot  46  is positioned at an initial position of “6 O&#39;clock” and pushed into the enclosed portion of the housing  10 . Once fully inserted into the enclosed portion of the housing  10 , whereby the inside end  42  is positioned against the end  18  of the cavity  14 , and the indexing or exposed end  44  of the sonde  40  can be lowered into the cavity  14  and settled into position substantially inside the enclosed area of the housing  10 . Resilient collars  48 , such as O rings, are installed on the sonde  40  to center the sonde  40  within the cavity  14  and provide cushioning against mechanical shock. In the embodiment shown, for a typical sonde housing, approximately four inches of open space  100  (See  FIG. 2 ) should remain in the open area of the cavity  14  after the sonde  40  is installed in the cavity  14 . 
     Referring to  FIG. 2 , since the sonde  40  is to be “clocked” or indexed in respect to the drill bit&#39;s installed position, the sonde  40  may be rotated inside the cavity  14  to the desired position for indexing. In  FIG. 2 , a two-piece “clocking mechanism”  60  is installed into the housing  10  and attached to the sonde  40  via the keyway or slot  46  formed in the end of the sonde  40 . This clocking mechanism  60  secures the sonde  40  in the proper rotational relationship (calibration) and partially secures the sonde  40  in the housing  10 . The clocking mechanism  60  itself may then be secured with a first bolt  64 . First bolt  64  may be a socket head shoulder bolt. 
     Continuing with  FIG. 2 , once the clocking mechanism  60  is installed and secured with the first bolt  64 , the spacer  66  is inserted to fill the remaining open space  100  in the cavity  14 . The spacer  66  is designed with an extension or lip  67  that extends over the clocking mechanism  60  and a portion of the sonde  40  itself. The spacer  66  is secured to the bottom of the cavity  14  in the tapped hole  54  using the second bolt  70  and provides added measure of security for the sonde  40  should the door  80  (to be described) be lost. With the sonde  40 , clocking mechanism  60  and spacer  66  installed, somewhat less than about half the length of the sonde  40  is exposed if the door  80  is lost as compared to the exposure of the entire 18″ length of the sonde  40  when the prior art full length side load doors are lost. 
     The exploded view of the sonde housing  10  shown in  FIG. 2  includes a door  80  for enclosing and securing the sonde  40  within the cavity  14  of the housing  10 . The door  80  includes an exterior surface  90 , a machined hole  92  for passage of the third bolt  94  therethrough, and an edge  98  on either side of the door  80  that fits along the interior ledges  32  of the sonde housing  10  when the door  80  is in place. After securing the spacer  66 , the first end  82  of the door  80  with machined tab  86  is slid at an angle completely into the first notch  34  in the housing  10  and then slid in the opposite direction along the supporting interior ledges  32  (See  FIG. 1 ) within the bore  16  to engage the second tab  88  into the second notch  36 . The door  80  is then secured to the housing  10  using the third bolt  94 . The housing  10  may include tool joints  26 ,  28  on either end, as previously described. 
     Continuing with  FIG. 2 , a drill bit  102  having a threaded male end  104  is shown in an aligned position in preparation to be threaded into the female socket end of the tool joint  28  of the sonde housing  10 . 
     Referring to  FIG. 3 , an instrument housing  10  for a transmitter sonde  40  according to the present invention is shown with the sonde  40  installed and indexed or “clocked” within the housing  10  in a proper orientation to correspond to the position of the drill bit (not shown) as described herein above. It will also be observed that once the door  80  is placed in its final position, a slight gap  106  remains between the end  82  of the door  80  and the end of the opening  30  that receives the door  80 . However, only part of the tab  86  is exposed, the rest (and most) of its length remaining within the housing  10 . Also shown in  FIG. 3  is the ¾ inch (typically) “flush plug”  116  in place in the hole  24  provided.  FIG. 3  further illustrates the drill bit  102  installed in position tool joint  28 . 
     Referring to  FIGS. 4 and 5  there are illustrated cross sections of the sonde housing  10  with the transmitter sonde  40  installed, taken at the position indicated by the Roman Numerals IV and V respectively in  FIG. 3 .  FIGS. 4 and 5  depict respective embodiments of a sonde housing  10  having four water ports  110  disposed in the body  12  of the sonde housing  10  ( FIG. 4 ) and two water ports  110  disposed in the body  12  of the sonde housing  10  ( FIG. 5 ). The embodiment of  FIG. 4  is especially suited for sonde housings used with mud motors, which require relatively large volumes of water be pumped through the body of the sonde housing. The embodiment of  FIG. 5  is suited for drilling operations where a mud motor is not used. 
     While the invention has been shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof. For example, one version of the sonde housing  10  is available wherein the cross section may be any of three diameters adapted to 3.0″, 3.5″, and 4.5″ drill bits. The invention including its various component parts is readily scaled.