SAFETY PIN

The present invention relates to a safety pin for use in pinning one object, or component, to another. In more detail, the present invention relates to a fault tolerant safety pin that not only provides a visual indicator of a break in the pin but also retains the portions of the broken pin to each other. Although not limited in its scope to this particular use, the safety pin of present invention is particularly useful for pinning a Kelly Bushing into the Master Bushing during drilling operations.

A so-called Kelly Bushing is used to turn the Kelly and rotate the drill pipe during drilling operations. Drive pins are used on pin-type Kelly Bushings to connect, interface, or join the Kelly Bushing into the Master Bushing. A string of drill pipe (and the bit on the end of the drill string) is rotated for drilling operations by lowering the Kelly Bushing down into the Master Bushing and rotating the rotary table (with the Master Bushing installed inside the rotary table). The drill string may be very long, and therefore very heavy, so the pins are subjected to considerable stress. Drive pins sometimes break as a result of these stresses, and the bottom portion, or segment, of the broken pin sometimes falls to the drill floor when the Kelly Bushing is up in the derrick. As might be expected of a pin subjected to such stresses, the pins are substantial enough that personnel on the drill floor are at risk from the falling portion(s) of the broken drive pin when the Kelly Bushing has been raised above the drill floor. Depending upon the height from which it falls and the size of the broken portion, serious injury or death could result. It is also possible for the broken portion of the drive pin to fall into the well bore (even when the Kelly Bushing is not up in the derrick). It is therefore desirable to reduce the likelihood of either event, and it is an object of the present invention to provide a drive pin that reduces, or even eliminates, the risk of injury caused by a falling drive pin segment and/or the possibility of a segment of a broken pin falling into the well.

Another object of the present invention is to provide a drive pin that installs and operates in the same manner as industry standard drive pins for use in pinning the Kelly Bushing into the Master Bushing during drilling operations. Another object of the present invention is to provide a drive pin that reduces, or even eliminates, inspection and/or maintenance by providing a visual indicator of pin

failure. Another object of the present invention is to provide a pin that is used to pin any object to another object that provides a visual indicator of the failure of the pin and retains broken pin segments to each other to eliminate or reduce the likelihood of injury or damage and for inspection and maintenance of the pinned connection. In a broader sense, it is an object to provide a safety pin that is shaped and sized to function as a structural component for connecting two or more objects, or components, as a means of providing fault tolerance after a failure of the safety pin.

Other objects, and the many advantages of the present invention, will be made clear to those skilled in the art in the following description of the present invention and the drawings appended hereto. Those skilled in the art will recognize, however, that the embodiment described herein is only an example, provided for the purpose of describing the making and using of the present invention, and that it is not the only embodiment of a safety pin constructed in accordance with the teachings of the present invention.

The present invention addresses the above-described problem by providing a pin for joining one object to another. The safety pin comprises first and second portions manufactured in end-to-end relationship to each other to form an elongated member with the first and second bores extending part way into the respective first and second portions of the elongated member. A passageway extends through the elongated member to connect the first and second bores and a cable is positioned in the passageway and extends into the first and second bores to act as a tether for retaining the respective first and second portions to each other in the event of a break in the elongated member.

Referring now to the figures, Figure 1 shows a partially cutaway, partially sectional view of a safety pin constructed in accordance with the teachings of the present invention and indicated generally at reference numeral 10. Safety pin 10 is comprised of integral first and second portions 12, 14, machined to each other in end-to-end fashion to form a fault tolerant elongated member that is shaped in a manner suitable for pinning one object, or component, to another. In the embodiment shown, the elongated member is shaped for use in pinning the Kelly Bushing (not shown) to a Master Bushing (not shown) as known in the art for use in drilling operations, but those skilled in the art will recognize that the elongated member could be shaped and sized to, for instance, pin a

press, an antenna to a mast, or in any other application in which one object or component is joined or mounted to another. Similarly, the safety pin 10 shown in Figure 1 is formed of two portions of different diameters, each of approximately the same length and formed in the shape of a right cylinder because, as noted above, safety pin 10 is adapted for use in pinning a Kelly Bushing to a Master Bushing. Those skilled in the art will recognize that the first and second portions 12, 14 of the elongated member/safety pin 10 may be the same diameter, may be of different lengths, and may each be shaped differently from the other portion, in accordance with the particular component parts that are to be pinned or joined to each other by the safety pin of the present invention. A longitudinally-extending bore 16, 18 extends part way into the respective first and second portions 12, 14 of elongated member/safety pin 10, and a passageway 20 connects the first and second bores 16, 18. In the preferred embodiment shown, the first and second bores 16, 18 extend from opposite ends of the first and second portions 12, 14 toward each other, with passageway 20 positioned therebetween. It will be recognized from this disclosure, however, that bores 16, 18 need not open at the ends of the first or second portions and that there may be uses of safety pins constructed in accordance with the teachings of the present invention in which it is advantageous for the bores 16, 18 to open to the sides of the portions 12, 14. Either way, the openings of bores 16, 18 are preferably closed by plugs 22, and in the particularly preferred embodiment, the plugs 22 are made of a different material than the material comprising first and second portions 12, 14 of safety pin 10 and/or of a contrast color so as to provide a visual indicator that the pin is a safety pin of the type described herein (the same function can be accomplished by the color of the safety pin itself and/or by distinctive markings on the surface of the pin). It will also be recognized that the openings of bores 16, 18 need not even be closed for the safety pin of the present invention to function for its intended purpose; the plugs 22 are described herein are therefore not considered an essential element of the present invention. In the embodiment shown, the passageway 20 is of smaller diameter than the diameter of first and second bores 16, 18 for a purpose set out below.

A cable 24 is positioned in passageway 20 and extends into the first and second bores 16, 18. As can be seen from the portion of cable 24 that is shown in second bore ⁱ o ~,vι _A ^* >/« :„ «f u« _n _« lanπtVi λαn the loncrtVi r»f βflfptv nin 1 ω Tn one embodiment _, the

ends of cable 24 are anchored to first and second portions 12, 14 in first and second bores 16, 18; alternatively, the ends of cable 24 are anchored to the plugs 22 closing first and second bores 16, 18. In the embodiment shown, the ends of cable 24 are provided with caps 26 of a diameter larger than cable 24 and larger than the internal diameter (I. D.) of passageway 20. Regardless of whether cable 24 is anchored to first and second portions 12, 14 in bores 16, 18, anchored to plugs 22, or provided with caps 26 of larger diameter than the LD. of passageway 20, cable 24 functions as a tether to retain the first and second portions 12, 14 of safety pin 10 to each other in the event of a break at any point along the length of elongated member/safety pin 10. In the event of such a break, the longer length of cable 24 allows the first and second portions 12, 14 to separate, providing a visual indicator of pin failure while still retaining the two portions 12, 14 to each other.

Changes can be made to the component parts of the apparatus of the present invention without changing the manner in which the parts function and/or interact to achieve their intended result. By way of example, cable 24 need not be comprised of a metal cable or wire. Instead, cable 24 may be a chain, woven or braided belt of synthetic fiber, extruded or stranded polymer, or similar restraining tether. It will also be recognized that cable 24 need not pass through a smaller diameter passageway such that a single bore extends the entire length of safety pin 10 and is provided with an integral grate through which cable 24 extends, the ends of cable 24 being prevented from passing through the grate by an interference between the caps 26 on the ends of cable 24 and the metal grate. All that is needed to accomplish the function of retaining one portion of safety pin 10 to the other is an interference between structure on cable 24 and structure internal to one or the other, or both, of the first and second portions 12, 14 of safety pin 10 so that the two portions, or broken segments, of safety pin 10 are tethered to each other. It will also be recognized that the caps 26 need not be located at the ends of cable 24 and need not even be formed as caps. If, for instance, a woven or braided belt is used as the cable, the belt may be provided with knots at some location along its length to create the above-described interference between the belt and the first and second portions 12, 14 so as to retain the two portions of the safety pin to each other in the event of failure. All such changes, and others that will be clear to those skilled in the art, are ini»i«)« ^j 1 tn fall urithin th*» e/-r»rw» nf tfι<» fnllnwinσ nnn-limittnσ claims _.