FRETTING-WEAR RESISTANT BEACON LID

A connection system for a lid in a beacon housing. The lid is connected to the housing at a tab at a first end, after a lip of the lid is placed under a shelf at its second end. The tab has a cross-bore for receiving a connection pin through both the cross-bore and corresponding holes in the housing which form a continuous passage. The lid is placed under tension to reduce relative vibration between the lid and the housing. A set screw is placed within the tab to place a force on the connection pin. Further set screws are distributed about the lid and place the lid in tension relative to the housing. The lid can be removed by reducing the tension provided by the set screws, removing the connection pin, and adjusting the lid such that it is no longer under the shelf of the housing.

SUMMARY

The present invention is directed to an assembly. The assembly comprises a beacon, an elongate housing and a lid. The beacon is configured to emit a dipole magnetic field. The elongate housing extends from a first to a second end, and has an exterior surface within which a cavity is formed. The cavity receives the beacon and has an open mouth that joins the exterior surface of the housing. The lid is configured to close the mouth of the cavity. The lid comprises a tab defining a first and second bore. The first bore is non-parallel to and intersects the second bore. The elongate housing defines a pair of aligned bores, wherein the first bore of the tab forms a continuous passage with the pair of aligned bores when the lid is covering the mouth of the cavity.

In another aspect the invention is directed to a method of joining a lid to a housing. The housing has an open mouth exposing a cavity. The method comprises placing the lid over the open mouth, placing a pin through a first aperture in the housing, a first bore in the lid, and a second aperture in the housing, placing a set screw within a second bore in the lid, and placing a force on the pin with the set screw. The first bore, first aperture, and second aperture form a continuous passage when the lid is placed over the open mouth. The second bore is non-parallel to and intersecting with the first bore.

In another aspect the invention is directed to a method. The method comprises placing a beacon into a cavity in an elongate housing through an open mouth, covering the open mouth with a lid, securing the lid to the elongate housing with a component, and thereafter, placing a set screw into the lid such that placement of the set screw applies a force to the component.

DETAILED DESCRIPTION

In horizontal directional drilling (“HDD”) applications, a transmitter may be placed near a boring tool. Electromagnetic signals sent from the transmitter may be received at an above ground location to allow the path of the boring tool to be tracked and mapped. Typically, the transmitter is placed in a subassembly and protected from the underground environment. This subassembly is often called a “beacon housing.”

A typical beacon housing will allow the beacon to be placed such that electromagnetic tracking signals can be sent, but provides enough space for the operation of the boring tool to continue unabated. As a result, the beacon is often placed away from the centerline of a beacon housing, allowing more space for mechanical components such as drilling rods, or space for drilling fluid to be transmitted to the boring tool. As a result of this activity, and the boring activity itself, the beacon housing is subject to significant movement and vibration.

Small amplitude wear between a below-ground beacon housing and the lid through which a beacon is installed into that housing, may cause wear to the lid. This wear, referred to herein as “fretting”, also results in components, such as bolts and other fasteners used to retain the lid, to loosen and wear as well, amplifying the problem as the apparatus is used.

The apparatus described herein places one or more adjustable screws along the length of the beacon housing lid to remove the slack from the system. By pre-loading the components, relative vibration is minimized and fretting wear reduced.

In current beacon housings, a lip is utilized to provide retention at one end, with a bolt or other fastener at the other. The current invention utilizes set screws, as shown in the figures, to place these components in shear and compression, while putting the set screws in compression as well, which avoids the need to remove the screws.

Turning now to the figures, a beacon housing10is shown therein. The beacon housing10extends from a first end12to a second end14. Formed thereon, and extending between the first12and second14ends, is a housing lid20. The housing lid20is adapted to cover a cavity18formed in the beacon housing10, in which a beacon may be placed. One or more cutting teeth16may be disposed near the second, or downhole end14.

The lid, as best shown inFIGS.2,4and8, extends from a first end22to a second end24. As shown, the lid20contains a narrow longitudinal slot21which promotes the transmission of an electromagnetic signal from the beacon to an above ground location with minimal impact on structural integrity of the beacon housing10.

At the first end22, a cross pin26or connection pin is placed through an aperture30in the housing10and an aperture32in the lid20to retain the lid20over the beacon cavity18. The aperture32and aperture30together form a cross hole, whereby the cross pin26, when fitted through the cross hole, prevents removal of the lid20.

A top hole40is disposed at the second end22of the lid20. The top hole40intersects the aperture30in the lid. A set screw42may be placed within the top hole40to apply a force to the cross pin26. The cross pin26may be a caliper bolt, heavy duty coil pin, or normal bolt, and is the only part required to be completely removed in order to detach the lid20from the housing10.

The set screw42may have a conical nose or another shape of nose configured for application of wedging forces to the cross pin26. The set screw42contacts the cross pin26at an angle, removing slack which may exist in the interface between the cross pin26and the lid20. Removing the slack reduces or eliminates fretting wear due to metal-to-metal vibration contact and prevents the cross pin26from backing out of the apertures30,32.

At the second end24a lip28may be placed below an overhanging shelf34on the housing10to provide retention. When installing the lid20, the lip28is placed under the shelf34, then the first end22is positioned such that the apertures30,32are aligned, allowing placement of the cross pin26.

Likewise, removing the cross pin26allows the first end22of the lid20to be pulled away from the housing10, and the lip28then pulled from under the shelf34. In order to remove the cross pin26, and thus the lid20, the set screw42need only be loosened to remove the tension on the cross pin, not removed entirely.

FIGS.7A and7Bshow the lid being removed without removing set screw42. InFIG.7B, the lid20is positioned in a second position, ready for connection to the housing10through the use of the cross pin26. However, as the cross pin26has been removed due to loosening of the set screw42, the lid20can be moved into a first position as shown inFIG.7A. The second end24may then be tilted away from the housing10and removed, allowing access to the cavity18.

The apparatus further comprises a plurality of lid set screws50. Each lid set screw50engages with a hole52. The lid set screws50are configured to engage against the housing10at various contact points, pushing the lid20away from the housing10. When the set screws50press against the housing10, pressure is applied to the lip28and the cross pin26, further protecting against fretting. In addition, these lid set screws50may engage with contact points such as depressions54formed in the housing10at the location where they engage, providing a locking mechanism. The set screws50may be loosened when the lid20is removed, as shown inFIGS.7A and7B.

Thus, the set screw42and lid set screws50have two general configurations. In the first configuration, the set screw42places a force on the cross-pin26and the lid set screws50extend to contact the housing at a contact point. This configuration places the lid20in tension as it is covering the cavity18. The cross-pin26is subjected to a shear force preventing its removal and the lid20itself is in tension due to the set screws50causing a force at the cross-pin26and the interface between the lip28and shelf34.

In a second configuration, the set screw42and lid set screws50do not apply a force—they are “loosened” from the first configuration. In this second configuration, the cross-pin26can be removed as desired, allowing the lid20to be adjusted such that the lip28is no longer under the shelf34of the housing, allowing removal of the lid20without the actual removal of any set screw.

Alternatively, or in addition to the set screws42,50used herein, a set screw may be placed at the second end24of the lid20to engage with lands formed in the housing10near the lip28. When set, such a set screw may provide force to cause the lid20to pop up when the cross pin26is removed, or may adjust the pressure between the lid20and housing10when the cross pin26is installed.

Finally, another alternative may involve set screws being used against a surface of the lid20, either at the first end22or second end24(or both), to reduce front-rear movement of the lid relative to the housing10. This orientation may be used alone or in combination with other elements disclosed herein. Preferably, the set screw42would be used with such a length-wise set screw arrangement.

Likewise, set screws may be used along the side of the lid, pushing the lid to one side and limiting movement in the same way. In this embodiment, the lid20has sideways play when placed above the cavity18. In one orientation, the lid may be placed such that it can be removed, but when moved to the side, it becomes locked in place. When this side-to-side play is removed (to decrease fretting), the lid may also be secured such that it remains placed over the cavity during operation.

The various features and alternative details of construction of the apparatuses described herein for the practice of the present technology will readily occur to the skilled artisan in view of the foregoing discussion, and it is to be understood that even though numerous characteristics and advantages of various embodiments of the present technology have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the technology, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present technology to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.