Field of the Invention

[001] This application relates generally to sensors and sensitive instruments and more particularly, but not by way of limitation, to a suspension system for supporting sensor components that resists shock and vibration.

Background

[002] Sensors are often susceptible to damage or performance degradation when exposed to mechanical shock and vibration. In downhole applications, sensor components must be made to withstand inhospitable conditions that include elevated temperatures, pressures and mechanical shock. Fragile sensor components must be suspended in a manner that will protect them from damage or performance failures when exposed to shock or vibration.

[003] In the past designers have suspended sensor components with leaf springs and wave springs to dampen shock and vibration. Although generally accepted, the use of leaf springs and wave springs complicates the manufacturing process and may produce inconsistent results. Accordingly, there is a need for an improved mechanism for suspending sensor components in a downhole environment. It is to this and other needs that the preferred embodiments are directed.

Summary of the Invention

[004] Preferred embodiments of the present invention include a suspension assembly for supporting a shock-sensitive component includes an outer housing and one or more radial canted coil springs that surround and support the shock-sensitive component. Each of the plurality of radial canted coil springs is preferably a toroid. The exterior of each of the plurality of radial canted coil springs is in contact with the outer housing and the interior of each of the plurality of canted radial canted coil springs is in contact with the exterior of the shock-sensitive component. The radial canted coil springs dampen mechanical shock and vibration applied in a lateral direction. The suspension assembly optionally includes an axial canted coil spring that dampens mechanical shock in the axial direction. The outer housing may include grooves that locate the radial canted coil springs within the suspension assembly.

[005] In another preferred embodiment, the present invention includes a downhole instrument for measuring a condition in a wellbore. The downhole instrument includes a sensor module, which in turn includes a sensor and a suspension assembly that supports to sensor within the sensor module. The suspension assembly preferably includes an outer housing that contains the sensor, an annulus between the interior surface of the outer housing and the sensor, and a plurality of radial coiled springs. Each of the plurality of radial coiled springs preferably comprises a toroidal coiled spring that is positioned within the annulus between the outer housing and the sensor. The suspension assembly optionally includes an axial coiled spring.

Brief Description of the Drawings

[006] FIG. 1 is an elevational view of a downhole instrument constructed in accordance with a preferred embodiment.

[007] FIG. 2 is cross-sectional elevational view of the suspension assembly of the downhole instrument of FIG. 1. [008] FIG. 3 is cross-sectional top view of the suspension assembly of the downhole instrument of FIG. 2.

[009] FIG. 4 is a perspective view of a toroidal canted coil spring of the suspension assembly of FIGS. 2 and 3.

Detailed Description of the Preferred Embodiment

[010] In accordance with a preferred embodiment of the present invention, FIG. 1 shows an elevational view of a downhole instrument 100 attached to a deployment cable 102. The downhole instrument 100 and deployment cable 102 are disposed in a wellbore 104, which is drilled for the production of a fluid such as water or petroleum. As used herein, the term "petroleum" refers broadly to all mineral hydrocarbons, such as crude oil, gas and combinations of oil and gas.

[011] The downhole instrument 100 includes a sensor module 106. The sensor module 106 may include sensors, analyzers, control systems, power systems, data processors and communication systems, all of which are well-known in the art. The deployment cable 102 connects the downhole instrument to surface-based facilities and provides power and communication to and from the downhole instrument 100. It will be appreciated that the downhole instrument 100 may alternatively be configured as part of a larger downhole assembly. For example, in an alternate preferred embodiment, the downhole instrument 100 is attached to a submersible pumping system or as part of a measurement while drilling system. If the downhole instrument 100 is incorporated within a measurement while drilling system, the instrument 100 may be powered by one or more batteries rather than through an umbilical extending to surface-based power supplies. Although demonstrated in a vertical wellbore 104, it will be appreciated that downhole instrument 100 may also be implemented in horizontal and non- vertical wellbores. The preferred embodiments may also find utility in surface pumping applications and in other applications in which a sensor or other sensitive component is exposed to the potential of shock and vibration.

[012] Turning to FIGS. 2 and 3, shown therein are elevational and top cross- sectional views, respectively, of a suspension assembly 108 constructed in accordance with a preferred embodiment. In the presently preferred embodiment, the suspension assembly 108 is incorporated within the sensor module 106. The suspension assembly 108 preferably includes an outer housing 110, one or more radial coiled springs 112, one or more axial coiled springs 114, a sealed cap 116, a locking ring 118 and a shock and vibration sensitive component 120. The space between the interior of the outer housing 110 and the exterior of the component 120 defines an annulus 122. The outer housing 110 preferably provides an access port 124 for making connections to the component 120.

[013] The component 120 is preferably selected from the group of sensitive components that includes scintillators, gamma ray detectors, x-ray detectors, accelerometers, photomultipliers, and other shock-sensitive components. It will be appreciated, however, that the component 120 could alternatively be selected from other mechanical, electrical or electro-mechanical devices and that the component 120 and suspension assembly 108 could be positioned outside the sensor module 106.

[014] The radial coiled springs 112 are sized and configured to occupy the annular space between the interior of the outer housing 110 and the exterior of the component 120. The axial coiled springs 114 are sized and configured to occupy the space between the end of the component 120 and the sealed cap 116. The radial and axial coiled springs 112, 114 are preferably toroidal and canted coiled springs that are constructed from a resilient metal. The canted coiled springs preferably exhibit a resilient and substantially uniform force that increases less than conventional springs during deflection. The exterior of each of the radial canted coil springs 112 is in contact with the outer housing 110 and the interior of each of the plurality of canted radial canted coil springs 112 is in contact with the exterior of the component 120. The suspension assembly 108 optionally includes a force distribution plate 130 positioned between the component 120 and the axial spring 114. The force distribution plate 130 more evenly distributes the application of forces between the axial spring 114 and the component 120.

[015] Turning to FIG. 4, shown therein is a front perspective view of a particularly preferred embodiment of the radial and axial coiled springs 112, 114. In the particularly preferred embodiment depicted in FIGS. 3 and 4, the radial and axial coiled springs 112, 114 include a polymer envelope 126 that entirely or partially encompasses the radial and axial coiled springs 112, 114. In highly preferred embodiments, the envelope is constructed from polytetrafluoroethylene (PTFE), which is available from a number of commercial sources. The envelope 126 protects the component 120 from direct contact with the radial and axial coiled springs 112, 114.

[016] The outer housing 110 preferably includes one or more grooves 128 at selected locations along the interior of the outer housing 110. The machined grooves 128 are preferably machined in the outer housing 110 and sized and configured to accept the one or more radial coiled springs 112. In the particularly preferred embodiment depicted in FIG. 2, the suspension assembly 108 includes three radial coiled springs 112, each disposed in a separate groove 128. The combined use of the radial coiled springs 112 and the grooves 128 facilitates the manufacturing process because the radial coiled springs 112 can more easily be located in the appropriate place within the suspension assembly 108.

[017] During use, the radial coiled springs 112 reduce mechanical shock applied from a lateral direction by absorbing a portion of the kinetic energy imparted on the suspension assembly 108. Similarly, when a shock is applied in the longitudinal direction, the axial coiled spring 114 absorbs a portion of the kinetic energy to reduce the shock applied to the component 120. The outer housing 110, the radial coiled springs 112 and the axial coiled springs 114 are preferably sized to permit the component 120 to deflect up to a predetermined threshold amount. Together, the outer housing 110, radial coiled springs 112 and axial coiled springs 114 provide a durable and resilient suspension system that is cost-effective and easy to manufacture.

[018] It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.