Safety apparatus for drilling rig

BACKGROUND OF THE INVENTION

The use of safety devices for automatically preventing the traveling block of a drilling rig from being pulled into the crown or top of the drilling rig and which is actuated by the cable that is coiled around the cable drum in order to control the rig clutch and brake is generally old as shown in U.S. Pat. Nos. 2,683,020 and 2,502,710. Thus, as the traveling block is raised a predetermined distance, the cable is wound on the cable drum and actuates an air toggle valve to in turn disengage the rig clutch and to engage the rig brake thereby stopping the traveling block a safe distance from the rig crown. Such prior art devices will automatically and safely stop the traveling block, but only at the same predetermined height position at which the apparatus is set. However, it is desired on many occasions to handle lengths of drill pipe or other special tools which are longer than standard such as drill collars. On such occasions, the safety device must be mechanically disassembled and deactuated in order to allow the rig to handle the longer strings of drill pipe. And, of course, if the safety device is not reassembled after completion of handling of the longer strings of drill pipe, the toggle valve will not protect the drill rig.

The present invention is directed to providing an improved apparatus in which the operator may override the automatic safety device so as to handle extra long lengths of drill pipe or drill collars but without disassembling the safety device. And while doing so the operator is made aware that he is overriding the automatic safety protection, and after the longer strings of pipe have been handled, the automatic safety device will again be ready to limit the movement of the traveling block.

SUMMARY

The present invention is directed to the improvement in an apparatus for preventing the traveling block of a drilling rig from being drawn into the crown of the rig in which a toggle valve controls the power to the rig brake and rig clutch by providing a manual override for allowing longer lengths of drill pipe to be handled by the drilling rig without actuation of the toggle valve.

Still a further object of the present invention is the provision of a manual override requiring the operator to maintain continuous actuation of the override so that he is constantly aware that he is bypassing the automatic safety stop of the toggle valve.

Still a further object is the provision of a manual override including a relay air valve connected to the toggle valve inlet with spring means normally holding the relay valve in the open position for supplying air to the toggle valve for automatic operation, but which when actuated closes the air supply to the toggle valve and vents the air from the toggle valve, and includes a second manually actuated valve for actuating the relay valve with spring means normally holding the second valve in the closed position.

BRIEF DESCRIPTION OFTHE DRAWING

FIG. 1 is a schematic view showing the apparatus of the present invention in position for automatically limiting the upward travel of the traveling block, and

FIG. 2 is a schematic view of the present invention in which the operator manually overcomes the automatic actuation of the toggle safety valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, and particularly FIG. 1, the reference numeral 10 generally indicates a drawworks drum of a conventional drilling rig on which a cable 12 is being wound. The drawworks is conventional and is part of a conventional drilling rig having a traveling block (not shown) which raises and lowers lengths of drilling pipe and no further description is believed to be necessary. The drum 10 is pro vided with a suitable power source (not shown) and a clutch 14 and brake 16, all of which is conventional. An air safety toggle valve 18 is provided positioned over the drum 10 and includes a stem 20 which is actuated when a sufficient number of turns of the cable 12 have been wound upon the drum 10 thereby indicating that the traveling block is at a predetermined level. A spring 23 normally holds a valve element 21 seated preventing passage of air from inlet 22 to outlet 26. Movement of the stem 20 moves valve element 21 to the open position as shown in FIG. 1 overcoming the spring 23 allowing passage of air through the toggle valve 18. The toggle switch is more fully described in U.S. Pat. No. 2,683,020.

The inlet 22 of the toggle valve 18 is connected to an air source. The outlet 26 of the toggle valve 18 is connected to the brake 16 and to a conventional relay valve 30, such as sold by C. Jim Stewart & Stevenson, Inc., Part No. 20100, which normally provides air from a source 32 to the clutch 14. Thus, when the toggle valve stem 20 is actuated by the cable 12, air will flow through the toggle valve 18 to actuate the relay valve 30 and deenergize the clutch 14 and will also flow to the brake 16 and actuate the brake.

A valve 24 is provided in the inlet line 22 of the toggle valve 18 with its outlet connected to the inlet of valve 18. Valve 24 is normally held in the open position by a spring and is closed and vented in the second position. Valve 24 is pneumatically moved to the second position and may be any conventional valve such as C. Jim Stewart & Stevenson, Inc. Part No. 20100. A manually actuated valve 40 is provided which is manually actuated by a lever 42 which is normally held in the closed and vented position 48 by a spring 44. Valve 40 is a two-way valve having an air inlet 46 connected to an air source. Valve 40 is moved to the open position 50 by manually actuating lever 42. Valve 40 is a conventional valve such as C. Jim Stewart & Stevenson, Inc. Valve No. 49600. The outlet from the valve 40 is connected to valve 24. When valve 40 is actuated, valve 24 is in turn pneumatically actuated. Valve 24 is a normally open valve as shown in FIG. 1 and includes an open position and a closed and vented position 62. Normally, the valve is in the open position as shown positioned in FIG. 1 by the action of spring 25 to allow the passage of air therethrough. However, when the valve 24 is actuated by the valve 40 and moved to the second position 62 passage of air to toggle valve 18 is stopped and in fact air is vented from the inlet 22 of the toggle 18 thereby preventing the toggle valve 18 from automatically stopping the drum 10 even though the stem 20 is engaged by a layer of cable 12.

Thus, when the operator desires to pull long strings of drill collars, drill pipe or special tools, the automatic acting toggle valve 18 can be deactuated by manually actuating valve 40 which will in turn actuate valve 24 which will block air from reaching the toggle 18 as well as venting the air at the inlet 22 of the toggle valve 18 so that even though the stem 20 of the toggle valve 18 is actuated the brake 16 is not set and the clutch 14 stays engaged. However, since the valve 40 is spring loaded, the operator must continuously hold valve 40 in the open position and therefore is constantly aware that the automatic acting toggle valve 18 is inoperative. Thus the operator knows so long as he is manually actuating valve 40 that he must be careful not to run the traveling block into the rig crown. If lever 42 is released, the automatic safety toggle valve 18 can be actuated.

After the special lengths of pipe have been handled, the stem 20 of the toggle valve 18 may be placed back in the vertical position thereby activating the valve 18 and valve 40 may be released thereby deactuating valve 24. The valves will then be returned to their initial position and the apparatus is ready to operate again automatically. The return of valve 40 to its original position by the spring 44 will bleed the air between valve 40 and valve 24 through the vent position 48 in valve 40 to atmosphere.

The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein.