Patent Description:
In underground drilling operations such as oil and gas drilling operations, it is often desirable to precisely control the drilling path of a new borehole relative to a known location (which may be disposed within the pathway of an existing borehole). To do that, operators may precisely monitor the location of the drill bit forming the new borehole relative to the existing borehole. For example, when a group of wells are drilled from an offshore platform, it is often necessary to drill new wells spaced three meters or less from existing wells for <NUM> meters or more during the initial depth interval. Subsequently, the wells may be directionally deviated and drilled to targets which may be two kilometers or more away in lateral directions. In another example application, this procedure may be useful when twin horizontal wells are drilled for the steam-assisted gravity drainage (SAGD) of heavy oils. In this example, it may be necessary to drill one well directly above the other while maintaining a five meter (±<NUM> meter) spacing over <NUM> meters of horizontal extension at depths of <NUM> or more meters. For example, the present invention may be employed in various types of underground drilling operations such as geothermal drilling, mining, hammer drilling and/or other such drilling operations. The present invention should not be deemed to be limited to the aforementioned examples.

The monitoring system used to control the drilling operations can include a magnetic field sensor that is disposed in the existing borehole and a magnetic source that is disposed in the new borehole. Specifically, the magnetic source assembly may be disposed in a drill string proximate the drill bit/tool. The magnetic source generates rotating magnetic fields perpendicular to the axis of rotation. The sensor apparatus typically includes a magnetometer assembly that is configured to measure the magnetic field radiating from the magnetic source assembly to precisely measure the location of the source. In this way, the drilling of the new borehole may be precisely controlled to achieve a desired separation between the existing borehole and the new borehole.

One issue that may be associated with a magnetic source assembly or a sensor assembly relates to their sensitivity to stress waves or thermal energy (heat). Briefly stated, the drilling process may generate stress waves and vibrational forces which propagate down the drill string to the magnetic source or sensor assembly. The stress waves may cause the magnetic source assembly or the sensor assembly to fail. The heat may be generated from various sources. Those skilled in the drilling/mining arts will appreciate that a drill bit may become relatively hot during mining and drilling operations. The thermal energy tends to cause the epoxy (and/or other potting compounds) used to secure the magnetic sources to the source assembly housing to be compromised or to fail entirely. As a result, the magnetic source elements may become loose or may begin to separate from the housing. Moreover, magnetic materials may lose their magnetic remanence if temperatures exceed the temperature rating of the magnetic material.

Another issue relates to rotationally registering the magnetic source assembly or the sensor assembly to the drill bit. Rotational registration allows the monitoring system to determine the orientation of the drill bit, as well the location of the drill bit, to more effectively control the drilling process. <CIT> discloses a downhole vibrational apparatus in line with the preamble of present claim <NUM>.

The present invention substantially addresses the needs described above by providing an apparatus and method configured to substantially isolate a downhole assembly from the stress waves or thermal energy experienced during drilling operations. The present invention is also configured to rotationally register a downhole assembly to a drill bit to thus provide drill bit orientation data during the drilling control operation.

One aspect of the present invention is directed to the assembly defined in claim <NUM>.

In one embodiment, the structural member includes a carrying region, a first shoulder member disposed at a first end portion of the carrying region and a second shoulder member disposed at a second end portion of the carrying region, wherein the housing member is coupled to the carrying region between the first shoulder member and the second shoulder member.

In one version of the embodiment, the structural member further comprises a box portion disposed at a first end of the structural member, a pin portion disposed at a second end of the structural member, and a carrying region being disposed between the box portion and the pin portion, the box portion being configured to accommodate a drive element of a drill string and the pin portion being configured to accommodate a tool bit or a drill bit.

In one embodiment, the structural member includes a first plurality of openings configured to provide the first pressurized fluid portion and a second plurality of openings configured to provide a second pressurized fluid portion.

In one version of the embodiment, the first plurality of openings are configured to direct the first pressurized fluid portion into the first pneumatic isolator and the second plurality of openings are configured to direct the second pressurized fluid portion into the second first pneumatic isolator.

In one embodiment, the at least one device includes at least one sensor device or at least one magnetic source element.

In one version of the embodiment, the at least one sensor device includes at least one accelerometer, a gyro sensor, a piezoelectric transducer, or a battery device.

In one embodiment, the at least one protective enclosure includes at least one set of pockets orientated in a plane perpendicular to the longitudinal axis, and wherein each pocket of the at least one set of pockets is configured to accommodate a magnetic source element.

In one embodiment, the pressurized fluid is a gas or a liquid.

In one embodiment, the structural member is a drill rod or a drill rod attachment.

In one embodiment, the external stress stimuli include stress waves, vibrations or thermal energy applied to the structural member.

In one embodiment, the pressurized fluid has a predetermined fluid pressure, the first pressurized fluid portion has a first variable fluid pressure, and the second pressurized fluid portion has a second variable fluid pressure, a sum of the first variable fluid pressure and the second variable fluid pressure being approximately equal to the predetermined fluid pressure.

In yet another aspect, the present invention is directed to a method as defined in claim <NUM>.

In one embodiment, the at least one device includes at least one sensor device or at least one magnetic source element, wherein the at least one sensor device includes at least one accelerometer, a gyro sensor, a piezoelectric transducer, or a battery device.

Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operation of the invention.

Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. An exemplary embodiment of the downhole assembly of the present invention is shown in <FIG>, and is designated generally throughout by reference numeral <NUM>.

As depicted in <FIG>, a cross-sectional view of a measurement system <NUM> featuring a magnetic source apparatus <NUM> and a magnetic field measurement sensor <NUM> is disclosed. As described below, the magnetic source apparatus <NUM> of the present invention can be equipped with pneumatic isolators <NUM>-<NUM> (shown and described below).

In <FIG>, the measurement system <NUM> is shown in the context of a pair of horizontal, spaced wells in accordance with an application of the present invention. This view illustrates a method and apparatus for guiding the directional drilling of a second borehole <NUM> relative to a first (previously drilled) borehole <NUM> such that the new borehole <NUM> is separated from the existing borehole <NUM> by a predetermined distance along their respective paths. The new borehole <NUM> contains a drill string <NUM> that carries or includes the magnetic source apparatus <NUM> (as well as the pneumatic isolator assembly). The drill assembly includes a drill bit <NUM> which is driven by suitable motors in a conventional manner, to rotate about a longitudinal axis of rotation and/or to reciprocate (axially hammer) along the longitudinal axis. The drill bit <NUM> may be steerable to control the drilling direction in response to control signals provided by a control station <NUM> located at the surface <NUM> (of the Earth). The magnetic source apparatus <NUM> includes a plurality of magnet elements <NUM> that generate an elliptically polarized rotating magnetic field <NUM> that is centered at the magnetic source apparatus <NUM> in the new borehole <NUM>. The magnetic source apparatus <NUM> includes a magnetic field source <NUM> which may be implemented using a permanent bar magnet <NUM> mounted in a non-magnetic portion of the assembly (not shown in this view) located at the distal end of the drill string behind the rotating drill bit <NUM>. The magnets <NUM> have north-south axes that are perpendicular to the longitudinal axis <NUM> of the drill bit <NUM>. Because assembly <NUM> rotates (and/or reciprocates) about the longitudinal axis <NUM> with the drill bit <NUM>, the elliptically polarized magnetic field <NUM> is an alternating magnetic field at observation point <NUM> (which is radially spaced from the magnets <NUM>).

The existing borehole <NUM> is illustrative of a horizontal well of the type which may be used for steam assisted gravity drainage of heavy oil (SADG). Of course, the present invention may be employed in any type of drilling application (and/or in any orientation) such as oil and gas drilling operations, geothermal, hammer drilling, top-hammer drilling, mining and/or other such drilling operations. In the example depicted in <FIG>, the drill bit <NUM> is controlled so that the borehole <NUM> is drilled directly above borehole <NUM> and is spaced above it by a predetermined, substantially constant distance. Control of the drill bit <NUM> is carried out in response to measurements made in the target borehole <NUM> by a magnetic field sensor <NUM>. The measuring tool <NUM> is lowered into the borehole <NUM> through a casing by means of a suitable wireline <NUM>, with the location, or depth, of the measuring tool being controlled from the earth's surface in conventional manner from an equipment truck <NUM>.

Again, the magnetic field sensor <NUM> is located at an observation point <NUM> and may incorporate a pair of fluxgate magnetometers having their axes of maximum sensitivity intersecting each other at the observation point and at right angles to each other. The magnetometers measure the amplitude and the phase of two perpendicular components of the magnetic field <NUM>. The measuring tool <NUM> may also include additional sensors such as earth's field sensors, inclinometers, and/or a gyroscope (depending on the application).

As embodied herein and depicted in <FIG>, a cross-sectional view of a pair of horizontal, spaced boreholes in accordance with another application of the present invention is disclosed. In this example application, a rock drilling assembly <NUM> employs a movable carrier <NUM> having one or more booms <NUM>-<NUM> connected to the carrier <NUM>. A drilling unit <NUM>-<NUM> may be disposed at the distal end of the boom <NUM>-<NUM>. The drilling unit <NUM>-<NUM> may comprise a feed beam <NUM>-<NUM> and a rock drilling machine <NUM>-<NUM> which drives the drill rod <NUM> and hence drill bit <NUM> into a rock wall <NUM>. In this application the drilling assembly is used to form a series of boreholes in the rock face, wherein each borehole is formed such that it follows a predetermined path in three-dimensional space within the rock wall/structure <NUM>.

Like the application depicted at <FIG>, the measurement system <NUM> features a magnetic source apparatus <NUM> (that includes the pneumatic isolator assembly) and a magnetic field measurement sensor <NUM>. In this application, a cross-sectional view of a pair of horizontal, spaced boreholes is shown. Like the previous application shown at <FIG>, this view illustrates a method and apparatus for guiding the directional drilling of a second borehole <NUM> relative to a first (previously drilled) borehole <NUM> such that the new borehole <NUM> is separated from the existing borehole <NUM> by a predetermined distance along their respective paths. The new borehole <NUM> contains the magnetic source apparatus <NUM>. As before, the magnetic field sensor <NUM>, located at an observation point <NUM>, and may incorporate a pair of fluxgate magnetometers having their axes of maximum sensitivity intersecting each other at the observation point and at right angles to each other. The magnetometers measure the amplitude and the phase of two perpendicular components of the magnetic field <NUM>. The measuring tool <NUM> may also include additional sensors such as earth's field sensors, inclinometers, and/or a gyroscope (again, depending on the application).

As embodied herein and depicted in <FIG>, a diagrammatic depiction of a downhole assembly <NUM> (equipped with a pneumatic isolator assembly) in accordance with an embodiment of the present invention is disclosed. The downhole assembly <NUM> may include a drill rod <NUM>, which is typically employed in the example applications depicted at <FIG>. (As noted above, the present invention should not be deemed to be limited to the example applications depicted at <FIG>. One skilled in the art will appreciate that the present invention may be employed in other applications and, thus, the drill rod may be implemented using any structural member suitable for the application at hand).

The drill rod <NUM> (or structural member) includes shoulder members (<NUM>-<NUM>, <NUM>-<NUM>) that are used to accommodate a downhole housing <NUM> disposed therebetween. The drill rod <NUM> may include a box portion <NUM>-<NUM> at one end thereof, and a pin portion <NUM>-<NUM> at second, opposite end thereof. The box portion <NUM>-<NUM> may be configured to accommodate a drive member associated with the drilling assembly <NUM>. The pin portion <NUM>-<NUM> may be configured to accommodate a drill bit or some other tool suitable for the instant application.

The downhole housing <NUM> includes a first housing portion <NUM>-<NUM> and a second housing portion <NUM>-<NUM>. In the magnetic source embodiment, each housing portion (<NUM>-<NUM>, <NUM>-<NUM>) includes magnetic field source elements (e.g., permanent magnets) <NUM> (not shown in this view) that are configured to generate magnetic field <NUM> (as shown at <FIG>). In the sensor assembly embodiment, and as described below, the portions (<NUM>-<NUM>, <NUM>-<NUM>) may include a power supply and or battery, a gyro sensor, accelerometers, rotational sensors, receiver, transmitter, a controller and/or memory. During assembly, the first housing portion <NUM>-<NUM> is coupled to the second housing portion <NUM>-<NUM> by connector elements which are disposed in connector vias <NUM>-<NUM>. Once the first housing portion <NUM>-<NUM> is coupled to the second housing portion <NUM>-<NUM>, the downhole housing <NUM> is spatially registered to the tool face of any bit or tool coupled to the pin portion <NUM>-<NUM>. A pneumatic isolator portion <NUM>-<NUM> is formed at each end of the housing <NUM>. The downhole housing <NUM> may be disposed within a non-magnetic cover <NUM> that is fastened to the housing <NUM> using any suitable fastener elements (e.g., screws, rivets, etc.). The interior configuration of the downhole housing <NUM> is described in greater detail below in conjunction with <FIG>.

In reference to <FIG>, a detail view of the drill rod portion <NUM> of the downhole apparatus <NUM> depicted in <FIG> is disclosed. The drill rod <NUM> includes a source/sensor carrying region <NUM>-<NUM> disposed between the shoulder members (<NUM>-<NUM>, <NUM>-<NUM>). (Depending on the housing embodiment, region <NUM>-<NUM> either carries a magnetic source housing or a sensor housing). The source/sensor carrying region <NUM>-<NUM> is used to accommodate the downhole housing <NUM> thereon. As before, the drill rod <NUM> may include a box portion <NUM>-<NUM> at one end thereof, and a pin portion <NUM>-<NUM> at second, opposite end thereof. Fluid channels <NUM>-<NUM> are disposed within the payload carrying region <NUM>-<NUM> substantially adjacent to the shoulder members (<NUM>-<NUM>, <NUM>-<NUM>). In one embodiment, the fluid channels <NUM>-<NUM> are disposed at equidistant points around the drill rod circumference (e.g., eight channels spaced apart in <NUM>° increments). Those skilled in the art will appreciate that the size and number of the fluid channels <NUM>-<NUM> may depend on the fluid traversing the channels (e.g., air, water, etc.), as well as the application for which the assembly is being used. Accordingly, more or less channels <NUM>-<NUM> may be employed depending on the embodiment and/or application. For example, the number and size of the fluid channels may correspond to fluid (air) pressure requirements of the pneumatic isolators <NUM>-<NUM>.

The source/sensor carrying region <NUM>-<NUM> may be characterized by a hexagonal cross-section in one embodiment thereof (<FIG>). In another embodiment, the source/sensor carrying region <NUM>-<NUM> may be characterized by an irregularly-shaped cross-section (as shown at <FIG>).

In one embodiment, the drill rod <NUM> is formed by a machining a steel alloy billet (e.g., using a CNC milling machine) to produce an integrally formed drill rod. In another alternate embodiment, the shoulder members (<NUM>-<NUM>, <NUM>-<NUM>) may be formed on a steel alloy rod using a sputter-welding process, wherein layers of steel material are deposited and built-up along the circumference of the rod at appropriate locations. The built-up portions are then machined (using, e.g., a lathe) to form the shoulder portions (<NUM>-<NUM>, <NUM>-<NUM>). The box portion <NUM>-<NUM> and the pin portion <NUM>-<NUM> may be welded to their respective ends of the drill rod <NUM> by way of a friction-welding process. In the various alternate embodiments, those of ordinary skill in the art will appreciate that the shoulders (<NUM>-<NUM>, <NUM>-<NUM>), pin <NUM>-<NUM>, box <NUM>-<NUM>, and other such features may be formed and/or machined using any suitable fabrication method(s).

In one embodiment of the present invention, the drill rod may be formed using a chrome-molybdenum AISI Alloy <NUM> steel bar (which has, e.g., a tensile strength of about <NUM> x <NUM><NUM> Pa (<NUM>,<NUM> psi), an elastic modulus within a range of about <NUM>,<NUM> - <NUM>,<NUM> ksi, and a Brinell hardness of about <NUM>). Thus, chrome-molybdenum AISI Alloy <NUM> steel bars may be employed in each of the fabrication and machining embodiments described above.

As embodied herein and depicted in <FIG>, an isometric view of a magnetic source housing <NUM> depicted in <FIG> is disclosed. The non-magnetic cover <NUM> is shown in a cut-away view to show the first housing portion <NUM>-<NUM> and the connector vias <NUM>-<NUM> disposed there within. The non-magnetic cover <NUM> may be formed using any suitable non-magnetic material including stainless steel, titanium, BeCu, aluminum, etc..

In one embodiment, the magnetic source housing <NUM> may be formed from a cylindrical or tube-shaped material (hereinafter "stock material") that is divided into two halves to form the first housing portion <NUM>-<NUM> and the second housing portion <NUM>-<NUM>. In one embodiment, the stock material may be comprised of a Teflon PTFE resin material that substantially complies with UL 94V0 and ASTM D1710 standards. In other embodiments, the tube material may be comprised of any suitable material; for example, the material may be an acetal homopolymer (Polyoxymethylene POM) material sometimes known as Delrin. In another example, the material may be a Polyether ether ketone (PEEK) material, which is a colorless, organic, thermoplastic polymer. In yet another embodiment, the material may be bronze or a bronze alloy material. Those skilled in the art will appreciate that the materials of the tube used to form the magnetic source housing <NUM> may vary in accordance with the application since the environment (vibrations, shock, temperature, etc.) may also differ from application to application.

In one embodiment, the stock material may have an outer diameter (OD) of about <NUM> (<NUM> inches), an inner diameter (ID) of about <NUM> (two inches), and a wall thickness of about <NUM> (one inch). Those of ordinary skill in the art will appreciate that the dimensions of the stock material used to form the downhole housing <NUM> may vary in accordance with the embodiment and/or application.

Referring back to <FIG>, before the stock material is separated into two parts (i.e., to form the first housing portion <NUM>-<NUM> and the second housing portion <NUM>-<NUM>), the stock material may be machined to include the various features depicted at <FIG>. For example, the stock material may be machined to include the connector vias <NUM>-<NUM>, magnetic source pockets <NUM>-<NUM>, sensor assembly pockets <NUM>-<NUM> (See <FIG>), the pneumatic isolator portion <NUM>-<NUM> and its constituent elements. The connector vias <NUM>-<NUM> may be configured to accommodate any suitable fastener element (e.g., a pop-rivet, etc.) for connecting the first housing portion <NUM>-<NUM> to the second housing portion <NUM>-<NUM> during assembly; i.e., when the downhole housing <NUM> is coupled to the source/sensor carrying region <NUM>-<NUM> of the drill rod. Alternatively, some or all of the features may be machined after the stock material is separated into two parts.

The pneumatic isolator portion <NUM>-<NUM> includes a piston-chamber <NUM>-<NUM> formed by a rim <NUM>-<NUM> that extends outwardly and perpendicularly from the inner abutment wall <NUM>-<NUM> by a distance "R. " Each pneumatic isolator portion <NUM>-<NUM> also includes a housing registration feature <NUM>-<NUM> (which is described in greater detail below). Note that each end of the downhole housing <NUM> includes a pneumatic isolator <NUM>-<NUM>.

Each magnetic source pocket <NUM>-<NUM> is configured to accommodate a magnetic source element <NUM> and an epoxy (or other) potting material. The potting material is employed to hold the magnetic element <NUM> in place within its respective pocket <NUM>-<NUM>.

The magnetic sources <NUM> employed in the invention may vary in accordance with the application since the environment (vibrations, shock, temperature, etc.) or desired operating parameters may also change in accordance with the application. Some non-limiting examples of operating parameters may be remanence, coercivity, Curie temperature, and etc. Accordingly, the magnetic source elements <NUM> may be implemented using neodymium rare earth magnets, samarium cobalt magnets or any suitable magnetic source elements depending on the application.

As described herein, the registration feature <NUM>-<NUM> may be configured as a hexagonally-shaped channel that is machined (or otherwise formed) to accommodate a hexagonally-shaped source-carrying region <NUM>-<NUM> of the drill rod there within. (Note that registration feature and source-carrying region <NUM>-<NUM> may be machined to conform to any suitable geometry and is thus not limited to a hexagonal shape; see, e.g., <FIG>). Consequently, the registration feature <NUM>-<NUM> conforms to the source-carrying region <NUM>-<NUM> of the drill rod such that the downhole housing <NUM> is in a fixed spatial relationship (i.e., it is registered to) to the drill rod <NUM> in at least two-dimensions. On the other hand, (cf. <FIG>, <FIG>, and <FIG>) note that the downhole housing <NUM> is configured to slide along the source-carrying region <NUM>-<NUM> between the two shoulders (<NUM>-<NUM>, <NUM>-<NUM>) in a substantially frictionless manner. The maximum sliding distance at each end of the housing <NUM> is equal to the distance "R," which is the distance from the abutment wall <NUM>-<NUM> to the rim <NUM>-<NUM>. Consequently, the magnetic field <NUM> measurements taken by the sensor <NUM> (at <FIG>) are not affected by the movement because the magnetic source elements <NUM> can only slide a maximum distance of about "2R" along the longitudinal axis. Stated briefly, therefore, the downhole housing <NUM> is substantially registered to the drill rod <NUM> (and hence to a tool face connected to the drill rod) in three-dimensional space.

In some embodiments, the housing <NUM> may include an O-ring (not shown at <FIG>) that seals the volume formed by the registration feature <NUM>-<NUM> from the piston-chambers <NUM>-<NUM>. Stated differently, an O-ring may be positioned at each end of the registration feature <NUM>-<NUM>. The O-ring is configured to seal the interior of the registration feature <NUM>-<NUM> when or if it is packed with grease or some other lubricant material.

Referring to <FIG>, an isometric detail view of a sensor housing <NUM> depicted in <FIG> is disclosed. In this view, housing <NUM> is substantially the same as the source housing <NUM> depicted at <FIG>; accordingly, any description of like or similar elements are omitted for the sake of brevity. In this embodiment, each sensor pocket <NUM>-<NUM> is an enclosure configured to accommodate all or a portion of the sensor assembly <NUM> (as described herein) and an epoxy (or other) potting material. The potting material is employed to hold the sensor assembly <NUM> components in place within their respective pocket <NUM>-<NUM>.

Referring to <FIG>, a diagrammatic depiction of the sensor assembly depicted at <FIG> is disclosed. The sensor assembly <NUM> includes various modules coupled together by a bus system <NUM>-<NUM>. The bus system <NUM>-<NUM> is coupled to a microprocessor <NUM>-<NUM> and computer readable memory (CRM <NUM>-<NUM>). Moreover, the sensor assembly <NUM> also includes an accelerometer module (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) that is configured to sense three gravity direction (xyz) vector components. A gyro sensor <NUM>-<NUM> is configured to detect angular velocity and generate a commensurate angular rate signal. As those skilled in the art will appreciate, the gyroscope <NUM>-<NUM> is used for measuring the device's orientation and/or angular velocity.

The sensor assembly <NUM> also includes a piezoelectric transducer <NUM>-<NUM> that is configured to convert the mechanical energy (W) generated by the drilling operations into electrical energy. (An expression for the mechanical energy is provided below). As those skilled in the relevant arts would appreciate, the piezoelectric effect converts mechanical strain into electric current or voltage. The electrical current is provided to an electrical storage device <NUM>-<NUM> which includes a battery for storing the harvested energy. In an alternate embodiment, electrical power may be provided to the system <NUM> by way of wireline.

Finally, the sensor assembly <NUM> further includes a transmitter device <NUM>-<NUM> and a receiver <NUM>-<NUM>. The transmitter <NUM>-<NUM> and receiver may be configured as a wireless or as a wireline transceiver configured to communicate with an uphole telemetry system (not shown in this view). In one embodiment, the uphole telemetry system is configured to manipulate all of the sensor data provided by the sensor assembly <NUM> (disposed down-hole). This information, or some of the information, may be transmitted to a driller controller (<FIG>) so that an appropriate course correction can be made (if necessary). In another embodiment, data transfer may be effected when the device <NUM> is retrieved from the downhole environment.

The microprocessor <NUM>-<NUM> may be configured to bi-directionally communicate with the various components coupled to the bus <NUM>-<NUM>. In this embodiment, the microprocessor <NUM>-<NUM> may include on-board analog-to-digital conversion (ADC) channels that accommodate the analog output signals of the accelerometers (<NUM>-<NUM> - <NUM>-<NUM>). The analog output signal of the gyro sensor <NUM>-<NUM> may also be converted into digital signals.

The sizing and selection of the microprocessor <NUM>-<NUM> is considered to be within the skill of one of ordinary skill in the art with the following proviso: obviously, if the functionality of the up-hole control system is incorporated into the down-hole system, the computational burden of the resultant processor will necessarily be greater. In any event, in accordance with the embodiment of <FIG>, the microprocessor <NUM>-<NUM> may be implemented using any suitable processing device depending on processing speed, cost, and durability considerations. In one embodiment, therefore, processor <NUM>-<NUM> may be implemented using a <NUM> bit, a <NUM>-bit, a <NUM> bit, or any suitable microcontroller coupled to any suitable computer readable media <NUM>-<NUM>. As noted above, the microcontroller may be more or less powerful depending on cost/processing speed considerations.

The term "computer-readable medium" as used herein refers to any medium that participates in providing data and/or instructions to the processor <NUM>-<NUM> for execution. Such a medium may take many forms, including but not limited to RAM, PROM, EPROM, EEPROM, FLASH-EPROM or any suitable memory device, either disposed on-board the processor <NUM>-<NUM> or provided separately. In one embodiment, the processor <NUM>-<NUM> may include <NUM> KB of flash memory and <NUM> KB of SRAM.

In reference to <FIG>, a cross-sectional view of the magnetic source housing <NUM> through section A - A (as shown at <FIG>) is disclosed. In this view, the section is taken through the source/sensor carrying region <NUM>-<NUM> of the drill rod <NUM>. Note that a central fluid-flow channel <NUM>-<NUM> extends through the entire length of the drill rod <NUM> and is centered about the longitudinal axis <NUM> (see, e.g., <FIG>). The diameter of the central fluid-flow channel <NUM>-<NUM> is dimension "X;" in one embodiment, the dimension X may be about <NUM> (<NUM> inches). Dimension "Y" corresponds to the diameter of the source/sensor carrying region <NUM>-<NUM> before machining is performed. In one embodiment, the dimension Y may be about <NUM> (<NUM> inches). (The fluid transmitted through via <NUM>-<NUM> may be air of some other suitable fluid).

Note that in this view, the section taken through magnetic source housing <NUM> and cover <NUM> includes a set of four magnetic source elements <NUM>. Depending on the embodiment and/or application, the housing <NUM> may include up to ten (<NUM>) sets of four magnetic source elements <NUM>. In the embodiment shown at <FIG>, the housing <NUM> is characterized by a circular cross-section having a diameter of a dimension "Z". In one embodiment, the dimension Z may be about <NUM> (<NUM> inches).

In reference to <FIG>, a cross-sectional view of the downhole (source or sensor) housing <NUM> (through section B - B shown at <FIG>) is disclosed. In this view, the section is taken through a set of dual-connector vias <NUM>-<NUM>. A description of the drill rod <NUM>, the source/sensor carrying region <NUM>-<NUM>, and the downhole housing <NUM> is omitted (for the sake of brevity) because these elements are identical to the elements depicted in <FIG>. In any event, each connector via <NUM>-<NUM> is shown to include a rivet (e.g., a pop-rivet) that is configured to tightly couple the first housing portion <NUM>-<NUM> to the second housing portion <NUM>-<NUM> when they are coupled to the source/sensor carrying region <NUM>-<NUM>. Of course, any suitable connector may be employed.

In reference to <FIG>, a cross-sectional view of the magnetic source housing <NUM> (through section A - A shown at <FIG>) in accordance with an alternate embodiment of the present invention is disclosed. Note that in this embodiment the source/sensor carrying region <NUM>-<NUM> includes two sets of angled-planar regions <NUM>-<NUM> and two curvilinear regions <NUM>-<NUM>. While each planar region <NUM>-<NUM> is shown to accommodate a magnetic source element <NUM> in the sectional-view of <FIG>, in actuality, each planar region <NUM>-<NUM> accommodates a row of magnetic source elements (as region <NUM>-<NUM> extends into the page). Each curvilinear region <NUM>-<NUM> represents the circular cross-section of the drill rod <NUM> prior to machining; and thus, the curvilinear regions <NUM>-<NUM> are dimensionally characterized by a diameter of dimension Y (as described above).

In reference to <FIG>, a diagrammatic depiction of a sequence of steps in a top-hammer rock drilling operation is disclosed. In diagram <NUM>, a top hammer rock drill is shown to include a hammer/piston <NUM>-<NUM> that is used to impact the drill rod <NUM>. (See, e.g., <FIG>). The hammer <NUM>-<NUM> may be implemented using any suitable hammer type, e.g., such as a pneumatic hammer (which uses compressed air) or a hydraulic hammer (which uses pressurized hydraulic fluid). (The drill rod <NUM> is a diagrammatically depicted in this view as an elongated cylinder; in practice, however, the drill rod <NUM> may be of the type depicted at <FIG> and <FIG>).

During operations, the drilling motor <NUM>-<NUM> may simultaneously provide a reciprocating motion as well as a rotational motion to drive the drill rod <NUM>. The reciprocating motion provides the hammering action to the drill rod <NUM> while the rotational force slowly rotates the drill rod <NUM> and drill bit <NUM>. As the borehole length increases, additional drill rods are added to the drill string by screwing a new drill rod onto the drill string that extends into the borehole. The kinetic energy of hammering action is transmitted by the drill rod <NUM> to the drill bit <NUM> to thus fragment the rock <NUM> during the drilling action. Accordingly, any sensor instrument package or magnetic source package attached to a down-hole drill rod <NUM> must be able to with-stand intense stresses and strains. In this case, the pneumatic isolators are configured to substantially isolate the magnetic housing <NUM> from the stress, energy and power flow associated with the drilling.

In step <NUM>, the hammer <NUM>-<NUM> is shown prior to impact and is shown to have a length "L". In step <NUM>, the hammer <NUM>-<NUM> moves toward the drill rod <NUM> with a velocity v and strikes the drill rod <NUM>. In step <NUM>, a compressive stress wave Cp is generated in the hammer <NUM>-<NUM> and a compressive stress wave CH is also generated in the drill rod <NUM>. These stress waves are depicted in the diagram as an increased diameter in each element. The induced compressive stress (σ) is substantially equal to:
<MAT> Where, v is the velocity, E is Young's (elastic) modulus of the material (hammer and drill rod), and c is the speed of sound in the hammer/rod. This assumes that the diameter and material of the hammer <NUM>-<NUM> and the drill rod <NUM> are the same.

In step <NUM>, the stress wave Cp reaches the upper end of the hammer <NUM>-<NUM> and is reflected; and the compressive stress wave CH continues to propagate down the length of the drill rod <NUM>. In step <NUM>, the reflected wave Cp propagates down the hammer <NUM>-<NUM> and is transmitted into the drill rod <NUM> such that the stress waves CH and Cp are combined. In step <NUM>, the combined stress wave Cc exits the hammer <NUM>-<NUM>; and in response to being elastically compressed by the stress waves, the drill rod <NUM> has been displaced. The elastic compression (Δ) is substantially equal to: <MAT> In a typical top hammer application, Δ may be about <NUM> given a velocity (v) of <NUM>/s and a hammer length (L) of about <NUM>.

In step <NUM>, the stress wave has a length <NUM> and propagates along the drill rod <NUM> at the speed of sound c, which is substantially equal to <MAT> Where ρ is the density of the drill rod material. The stress wave propagates the mechanical energy W to the drill bit <NUM>, where <MAT> Wherein m is the mass of the hammer <NUM>-<NUM>. Of course, the mechanical energy W is the energy that fragments the rock <NUM> (<FIG>).

Referring to <FIG>, a chart showing a model of a stress wave resulting from a top-rock hammer drilling operation is described. Briefly stated, the stress wave curve <NUM> can be modeled as a sine wave or a cosine wave. The drill rod displacement curve <NUM> is integrated strain. Those skilled in the art will appreciate that the form of the stress wave <NUM> depends on the rock drill, drilling parameters, the number of drill rods <NUM> in a given drill string, the type of rock being drilled, the hardness and the integrity of the rock material, and etc. Nonetheless, the stress wave may be reasonably modeled as a sinusoid to ascertain the energy and forces being brought to bear on the downhole housing <NUM> described above.

In <FIG>, the displacement, velocity and acceleration curves for the strain associated with the stress wave depicted at <FIG> (and the top-hammer rock drilling operation described at <FIG>) are also shown. Note that the displacement curve <NUM> in <FIG> and the displacement curve <NUM> at <FIG> show similar subject matter but employ different horizontal axes.

In any event, the mathematical model makes the following assumptions: first, that the stress wave is sinusoidal, and second, that the geometry and material of the hammer <NUM>-<NUM> and drill rod <NUM> are substantially the same. Most importantly, they both have the same acoustic impedance. The model starts with the stress wave shown at step <NUM> of <FIG>. More formally, the drill rod <NUM> is modeled as a series of discrete rod elements; wherein each discrete element is characterized as having an appropriate mass and stiffness. Accordingly, the stress wave modeled by equation (<NUM>) is at some drill rod element "x" at time "t. " In step <NUM>, e.g., the impulse u(x, t) on the drill rod can be represented by: <MAT> Wherein u(x,t) is the tiny displacement of an element on the drill rod from its equilibrium location x at time t. The factor "(x - ct)" indicates that u(x, t) describes a displacement propagating along the longitudinal axis "x" of the drill rod <NUM> toward the drill bit <NUM>. While the shape of a wave pulse may assume any form, x and t must always appear in the combination with each other to satisfy the governing wave equation (i.e., the argument must include either (x - c•t) or (x + ct). If the argument is (x + ct), the stress wave displacement is propagating along the longitudinal axis "x" of the drill rod <NUM> toward the hammer <NUM>-<NUM> and away from the drill bit <NUM>.

Again, while equation (<NUM>) models the stress wave as a sinusoidal wave, those skilled in the art will appreciate that the wave could be modeled as a square wave or as a rectangular pulse. The factor <NUM> in equation (<NUM>) indicates that the wave packet has a length <NUM>, which corresponds to the hammer's length, as shown at step <NUM> of <FIG>.

Young's modulus of elasticity (E) is the ratio of stress (σ) over strain (ε), i.e., E = (σ/ε). Moreover, the strain (ε) is equal to du/dx. Accordingly, the stress wave σ associated with the wave element displacement u(x,t) may be expressed as: <MAT> Wherein E is Young's modulus of elasticity, which is about <NUM> x <NUM><NUM> N/m<NUM> for steel.

The velocity v of a molecule responding to the wave action is (du/dt); <MAT> Where ρ is the density of steel (<NUM> x <NUM><NUM> kg/m<NUM>; and the quantity (ρc) is known as the wave impedance.

The power S (per unit cross section area in watts/m<NUM>) being delivered to the drill bit is the stress (σ) times the velocity v, i.e., <MAT> <MAT> The power S (per unit cross section area (watts/m<NUM>)), is delivered for [(<NUM>)/c] seconds through each fixed location as it propagates through that location. Thus, the total energy W in the wave packet is found by integrating the power over the time interval [(<NUM>)/c]; i.e., during the time that the power S is flowing by a fixed location x on the drill rod <NUM>.

Thus, the total wave energy W passing by an observation point x is: <MAT> where <S> is the time average of the power S over the time interval (<NUM>/c).

The wave energy W is equal to the original kinetic energy (Wh) in the initiating hammer-blow, wherein Wh is given above at equation (<NUM>) as being equal to Wh = (<NUM>/<NUM>)mv<NUM>. From equation (<NUM>), the kinetic energy (Wh) may be expressed as: <MAT> Where m is the mass of the hammer <NUM>-<NUM>, ρ is the mass density of steel (about <NUM> x <NUM><NUM> kg/m<NUM>), v is the hammer velocity, A is the cross-section area of the hammer <NUM>-<NUM> (and drill rod <NUM>), and L is the length of the hammer <NUM>-<NUM>.

Equating the hammer energy Wh (equation <NUM>) to the wave energy (equation <NUM>) gives a solution for uo: <MAT> Note that uo is a relatively small displacement of one of the discrete drill rod elements referred to above during the discussion of the model parameters. Each of the other elements of equation (<NUM>) was described above.

Of course, the displacement uo may be substituted into some of the equations provided above to ascertain other properties of the propagating energy packet. Accordingly, the equation for the displacement uo in equation (<NUM>) may be substituted into equation (<NUM>) to obtain <MAT>.

The peak stress σ<NUM> occurs when x = ct; and thus the peak pressure σ<NUM> is simply the product of Young's modulus E, and the ratio of the hammer velocity v and the velocity of sound c in steel: <MAT>.

The equation for the wave velocity (du/dt) is given by equation (<NUM>) above as [(πc)/(<NUM>)] uo cos [(π/<NUM>)(x - ct)]. The expression for displacement uo may be substituted into equation (<NUM>) to provide: <MAT> <MAT> <MAT> Note that the sound wave displacement velocity du/dt is equal to the velocity of the hammer (v) immediately prior to the hammer's initial impact.

Considering the above analysis, some numerical examples are provided to illustrate some of the implications of the analysis to drilling and/or mining operations. Consider an example wherein the hammer has the following physical parameters: an <NUM> mass, <NUM> in length; and a <NUM> diameter. (Of course, the drill rod <NUM> would also include a <NUM> diameter in accordance with the modeling provided above). Moreover, the example further stipulates that the hammer percussion velocity v is about <NUM>/s. With these values, the original kinetic energy (Wh) would be about <NUM> joules per hammer blow, the displacement uo would be about <NUM> and the velocity v, i.e., du/dt, would be about <NUM>/s. The strain (ε), which equals du/dx, would be in a range of values between <NUM> and <NUM>. The stress (σ), which as shown above equals E• ε, would be in the range between <NUM> x <NUM><NUM> Pa - <NUM> x <NUM><NUM> Pa (<NUM> - <NUM>,<NUM> psi). Finally, the power <S>A is about <NUM>,<NUM> kW.

As noted above, the downhole housing <NUM> is configured to slide along the source-carrying region <NUM>-<NUM> between the two shoulders (<NUM>-<NUM>, <NUM>-<NUM>) in a substantially frictionless manner such that the stress wave and power flow are substantially not transmitted to housing <NUM>. Moreover, the pneumatic isolator portions <NUM>-<NUM> provide a pressurized and self-correcting air spring that substantially protects the housing <NUM> from any remaining portion of the stress wave and power flow that may be incident housing <NUM>. Also, the pneumatic isolator portions <NUM>-<NUM> at each end of the housing <NUM> provides cooling to housing <NUM> and substantially prevents dirt and debris from entering and occluding the frictionless interface (between housing <NUM> and region <NUM>-<NUM>).

As embodied herein and depicted in <FIG>, a diagrammatic depiction illustrating the operation of the apparatus <NUM> in response to a relatively high axial shock event is disclosed. Specifically, <FIG> illustrates how the pneumatic isolators <NUM>-<NUM> self-correct in response to a stress wave that disrupts an equilibrium state. Before describing the operations, note that the down hole housing <NUM> moves in response to a fluid-flow <NUM>-<NUM> directed through the central fluid-flow via <NUM>-<NUM>. In one embodiment, the fluid may be air that is forced through the central fluid-flow via <NUM>-<NUM> at about <NUM> x <NUM><NUM> Pa (<NUM> psi), at a volume/rate of about eight cubic meters per minute (<NUM><NUM>/min).

In this view, the housing <NUM> has been momentarily positioned by the stress wave in position A, which extends over the shoulder <NUM>-<NUM> such that the gap between the housing <NUM> and the drill rod shoulder <NUM>-<NUM> is substantially closed. Accordingly, the air-flow 40A that is expelled from the fluid channels <NUM>-<NUM> (proximate shoulder <NUM>-<NUM>) is directed against the piston abutment wall <NUM>-<NUM> to drive the housing <NUM> back toward shoulder <NUM>-<NUM> (and position B). At the opposite end of housing <NUM>, the air-flow 40B is expelled through the fluid channels <NUM>-<NUM> (proximate shoulder <NUM>-<NUM>) and the air pressure within this pneumatic isolator <NUM>-<NUM> (proximate shoulder <NUM>-<NUM>) is substantially decreased. On the other hand, the air-flow 40B acts to cool the housing <NUM> and substantially remove any debris from becoming lodged in the gap between the drill rod shoulder <NUM>-<NUM> and the rim <NUM>-<NUM>. Note that the pneumatic isolator portion <NUM>-<NUM> and the shoulder <NUM>-<NUM> typically do not come into contact; i.e., an air gap is typically maintained therebetween. Air gaps are also typically maintained between the carrying portion <NUM>-<NUM> and the registration portion <NUM>-<NUM> to facilitate a self-correcting sliding motion between position A and position B.

In similar fashion, once the gap between the pneumatic isolator portion <NUM>-<NUM> and the drill rod shoulder <NUM>-<NUM> begins to open (due to the self-regulating action of the pneumatic isolator <NUM>-<NUM>), the air-flow 40A that is expelled from the fluid channels <NUM>-<NUM> (proximate shoulder <NUM>-<NUM>) is expelled outwardly, and this action cools the housing <NUM> and substantially prevents debris from becoming lodged in the gap between the drill rod shoulder <NUM>-<NUM> and the housing <NUM>. At the other end of the housing <NUM>, the gap between the housing and the drill rod shoulder <NUM>-<NUM> begins to narrow so that the air-flow 40B is directed from the fluid channels <NUM>-<NUM> against the piston abutment wall <NUM>-<NUM> proximate shoulder <NUM>-<NUM>. At this point, the housing <NUM> is driven back toward shoulder <NUM>-<NUM> and position A. Again, note that the pneumatic isolator portion <NUM>-<NUM> and the shoulder <NUM>-<NUM> typically do not come into contact; an air gap is typically maintained therebetween. At this point, the pneumatic isolators <NUM>-<NUM> at each end of the housing <NUM> will continue to self-regulate until the housing <NUM> finds an equilibrium position.

As embodied herein and depicted in <FIG>, a diagrammatic depiction illustrating the operation of the apparatus in an equilibrium state is disclosed. In the equilibrium state, a series of stress waves may propagate down the drill rod <NUM> in response to operational stimuli. The pneumatic isolators <NUM>-<NUM> formed at each end of the housing <NUM> employ pressurized air chambers <NUM>-<NUM> that facilitate the equilibrium state. In the equilibrium state, the rim portion <NUM>-<NUM> at each end (A, B) overlaps its respective shoulder (<NUM>-<NUM>, <NUM>-<NUM>) by a relatively small distance. Thus, there is a small amount of fluid (air) leakage from the fluid (air) vias <NUM>-<NUM> disposed inside each air chambers <NUM>-<NUM>. Thus, each pneumatic isolator chamber <NUM>-<NUM> is pressurized at a substantial fraction of the pressure of the fluid flowing in the drill rod. By way of example, each chamber may be pressurized at a substantial fraction of a <NUM> x <NUM><NUM> Pa (<NUM> psi) air stream <NUM>-<NUM> flowing in the center drill rod via <NUM>-<NUM>; i.e., a pressure a little less than <NUM> x <NUM><NUM> Pa (<NUM> PSI). The air supply channels <NUM>-<NUM> on the drill rod region <NUM>-<NUM> are appropriately sized to direct an air flow amount into the chamber <NUM>-<NUM> that is substantially the same air flow amount that leaks from the gap between each rim portion <NUM>-<NUM> and its respective shoulder (<NUM>-<NUM>, <NUM>-<NUM>).

Accordingly, when the housing <NUM> slides slightly toward position A, a relatively small gap may be formed between the drill rod shoulder <NUM>-<NUM> and its respective rim <NUM>-<NUM> (i.e., at position B) and the gap will result in an increase in air leakage and a drop in air pressure in the chamber <NUM>-<NUM> (at position B). In the pneumatic isolator chamber <NUM>-<NUM> at the opposite end proximate shoulder <NUM>-<NUM> (position A), there is a decrease in air leakage and an increase in the air pressure; as such, the increased air pressure causes the housing <NUM> to slide in the opposite direction to close the gap and equalize the air pressure. If the housing <NUM> slides slightly toward position B, a similar process occurs to maintain the self-correcting equilibrium. Again, in this example, each air chamber <NUM>-<NUM> is supplied with up to about <NUM> x <NUM><NUM> Pa (<NUM> psi) of air pressure to maintain an equilibrium state, and thus implements a pneumatic spring that is not subject to fatigue or failure at connection points and/or concentrated points of intense acceleration.

In summary, the housing <NUM> operates in a self-correcting manner to reciprocate (in a frictionless manner) between drill-rod shoulder <NUM>-<NUM> (position A) and drill-rod shoulder <NUM>-<NUM> (position B) at a relatively high rate. In doing so, the pneumatic isolator portion <NUM>-<NUM> at each end of the housing <NUM> alternate between a first (drive) mode and a second (cooling and debris removal) mode. The present invention substantially prevents thermal energy, stress wave and vibrational forces (e.g., from drilling and/or hammer-drilling) from being transmitted from the drill rod <NUM> to the housing <NUM> by virtue of the air (fluid) gap that is maintained between the drill rod <NUM> and housing <NUM>. Those skilled in the art will appreciate that F = ma; i.e., force equals mass times acceleration. In this case, when a drill bit is hammered against a rock wall (see, e.g., <FIG>), the force is reflected and a shock wave is transmitted by the steel mass toward the housing <NUM>. Once the force is incident the steel-air (fluid) boundary that characterizes the interface between the housing <NUM> and the drill <NUM>, the magnitude of the force drops precipitously because the mass of the air (fluid) is orders of magnitude lower than the mass of the steel.

With regard to transmitting thermal energy, a similar principle is at play. Specifically, steel is an excellent conductor of heat whereas air (fluid) functions as an insulator that does not readily conduct heat from the steel rod <NUM> to the housing <NUM>. Moreover, the heat is further prevented from being transmitted from the drill rod <NUM> to the housing <NUM> by the cooling action of the fluid channels <NUM>-<NUM> (as described previously).

Note also that while the housing moves about the drill rod <NUM> in the manner thus described, the drill rod <NUM> is typically rotating and/or reciprocating due to drive forces applied at the drive box <NUM>-<NUM> (<FIG>). Despite this drill rod motion, the housing <NUM> maintains rotational registration to the drill rod <NUM> such that a rotational position of a tool face (coupled to the drill rod pin <NUM>-<NUM>) may be ascertained at all times (as a function of the rotational position of the magnets <NUM>).

While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto; inventive embodiments may be practiced otherwise than as specifically described and claimed.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The term "connected" is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening.

Accordingly, a value modified by a term or terms, such as "about" and "substantially", are not to be limited to the precise value specified. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.

The recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein.

The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate embodiments of the invention and does not impose a limitation on the scope of the invention unless otherwise claimed.

Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as set forth in the <NPL>.

Claim 1:
An assembly comprising:
a structural member (<NUM>) having a longitudinal axis (<NUM>) and configured to conduct a pressurized fluid in an operational state; and
an apparatus (<NUM>) comprising
a housing member (<NUM>) including a first end, a second end, and at least one protective enclosure (<NUM>) configured to accommodate at least one device, the housing member (<NUM>) being configured to move on the structural member (<NUM>) parallel to the longitudinal axis (<NUM>) in the operational state with a substantially frictionless reciprocating motion, the housing member (<NUM>) being rotationally registered to the structural member (<NUM>),
a first pneumatic isolator (<NUM>-<NUM>) formed at the first end, and
a second pneumatic isolator (<NUM>-<NUM>) formed at the second end,
characterized in that
the apparatus (<NUM>) is adapted to apply a first pressurized fluid portion of the pressurized fluid to the first pneumatic isolator (<NUM>-<NUM>) in the operational state to drive the housing member (<NUM>) toward a second direction of the reciprocating motion,
the apparatus (<NUM>) is adapted to apply a second pressurized fluid portion of the pressurized fluid to the second pneumatic isolator (<NUM>-<NUM>) in the operational state to drive the housing member (<NUM>) toward a first direction of the reciprocating motion opposite the second direction, and
the substantially frictionless reciprocating motion is a function of external stimuli, the first pressurized fluid portion and the second pressurized fluid portion, wherein the housing member (<NUM>) is substantially isolated from the external stimuli.