US3881375A

US3881375A - Pipe tong positioning system

Info

Publication number: US3881375A
Application number: US314285A
Authority: US
Inventors: Robert R Kelly
Original assignee: Borg Warner Corp
Current assignee: Varco International Inc
Priority date: 1972-12-12
Filing date: 1972-12-12
Publication date: 1975-05-06
Anticipated expiration: 1992-05-06
Also published as: US3882377A; FR2327386A1; AT326592B; ATA1043173A; NL7316566A; GB1416245A; DE2357603B2; IT1000813B; FR2327386B1; CA984374A; RO70104A; JPS4989604A; DE2357603C3; DE2357603A1

Abstract

The combination of a power driven pipe tong and a backup tong is supported upon a hoist mechanism to be positioned vertically with respect to the tool joints of a string of drill pipe. A magnetic eddy current detector is disposed adjacent to the drill pipe and produces a command signal to control the hoist mechanism and stop motion when the tong assembly is in a position at which the tool joint engaging jaws of the power tong and the backup tong are properly engageable with the tool joints.

Description

United States Patent 1 Kelly [451 May 6,1975

[ PIPE TONG POSITIONING SYSTEM [75] lnventor: Robert R. Kelly, Hoffman Estates,

[73] Assignee: Borg-Warner Corporation, Chicago,

[22] Filed: Dec. 12, 1972 [21] Appl. No.: 314,285

[52] U.S. CI. 81/5735; 166/66; 324/37 [51] Int. Cl 1325b 13/50 [58] Field of Search 8l/57.l557.21,

81/57.3357.35; 324/37: 91/361, 363 R; 166/65 R, 65 M, 66, 77.5

[56] References Cited UNITED STATES PATENTS 2,714,874 8/1955 Hart 91/361 3,017,621 1/1962 Taborsky 324/37 3,103,976 9/1963 DeVries et a1. 166/46 3,194,313 7/1965 Fanshawe 166/775 X R 3,229,099 1/1966 Schwinghamer et 91/459 UX &

3,273,054 9/1966 Cook 324/37 3,361,961 l/1968 Zoellick... 324/40 3,435,614 4/1969 Ledeen et a1. 91/361 X R 3,465,241 9/1969 Metzger et a1 324/37 3,680,412 8/1972 Mayer et a1 81/5734 3,780,815 12/1973 Barron et 81/57.l6 X R Primary ExaminerAl Lawrence Smith Assistant Examiner-K. J. Ramsey Attorney, Agent, or Firm-Aubrey L. Burgess [5 7 ABSTRACT 13 Claims, 8 Drawing Figures PIPE TONG POSITIONING SYSTEM BACKGROUND OF THE INVENTION In the drilling of well bores, such as oil and gas wells, into the earth, and in other operations involving the completion, treatment or production of wells, a length of pipe is periodically round tripped. The drill string or string of pipe consists of stands which are made up of lengths of pipe, and the stands are successively made up or broken out of the string as the string is being run into and being removed from the well. During the drilling of the well, the well drilling pipe string is periodically round tripped for changing the bit at frequent intervals involving substantial labor and expense, and in order to facilitate the making up and breaking out of the so called tool joints between pipe stands, power tong apparatus has been developed comprising a power driven pipe gripping tong mechanism which is utilized in combination with a stationary backup pipe gripping tong mechanism engageable with the tool joint sections which are relatively rotatable to make up and break out the joints.

An example of such a combined power driven and backup tong is shown and described generally in the pending application for letters patent filed in the name of C. D. Barron, et al, Ser. No. 216,216, filed Jan. 7, 1962, for Power Tong Positioning Apparatus, now US. Pat. No. 3,780,815, issued Dec. 25, 1973, and assigned to the parent corporation of the wholly owned subsidiary corporation to which the present application is assigned, wherein the combined tong assembly is supported by a hoist mechanism so as to be positioned with respect to a string of drill pipe or the like, at a location at which the power operated pipe gripping mechanism and the backup pipe gripping mechanism are properly engageable with the tool joint sections.

In the manual control of such pipe tong positioning devices it is necessary that an operator visually correlate the tool joint with respect to the tong assembly as the latter is raised or lowered and be able to precisely position the tong assembly. However, it frequently occurs that the drilling and other well treating or producing activities are conducted during the night or during other periods when visibility is poor. Moreover, in the case of an automated drilling system it would be necessary that the tong assembly be properly positioned with respect to the tool joint in a pipe string in an automatic and accurate manner.

SUMMARY OF THE INVENTION The present invention involves utilizing sensing means carried by or adjacent to the combined power driven and backup tongs of a vertically movable tong assembly, the sensing means being operable to provide a control signal whereby vertical movement of the tong combination is arrested at a location at which the power driven tong and the backup tong are properly positioned for engagement of the tool joint engaging tong jaws with the tool joint parts of the pipe joint.

More particularly, the present invention involves the utilization of a magnetic eddy current responsive sensing unit which is adapted to provide a control signal whereby the hoist mechanism for a combined power driven tong and backup tong is controlled to properly position the tongs with respect to the tool joint parts.

In a specific sense, in accomplishing the foregoing, a magnetic eddy current sensing means is can'ied by the combined power driven and backup tong assembly and includes a probe supported in close proximity to the pipe, whereby when the interface between a pair of tool joint parts is detected due to the discontinuity, a control signal is supplied to de-energize the hoist operating means so that the tongs will be properly positioned with respect to the tool joints.

The joint detector is biased to a position with respect to the pipe so that the sensing head is adapted to be uniformally closely positioned relative to the tool joint over a range of tool joint diameters to compensate for worn, under-sized joints.

The tool joint detecting means may be combined with a set of power driven and backup tongs which are supported, by way of example, by the hoist mechanism of the aforementioned application for letters patent, Ser. No. 216,216, or by other hoist mechanism which is adapted to be controlled in response to the control signal transmitted thereto .by the sensing means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary view in side elevation with parts of the tong assembly broken away to disclose a tool joint therein;

FIG. 2 is an enlarged fragmentary detail view illustrating a typical drill pipe tool joint, portions of the tongs being shown in broken lines;

FIG. 3 is an enlarged horizontal section between the power tong and backup tong of FIG. 1, as taken on the plane of the line 33 of FIG. 1 and illustrating the disposition of the sensing means;

FIG. 4 is an enlarged fragmentary view in vertical section, as taken on the line 44 of FIG. 3;

FIG. 5 is an elevation of the end of the sensing means, as taken on the line 55 of FIG. 4;

FIG. 6 is a transverse section as taken on the line 6-6 of FIG. 4 and on a slightly enlarged scale;

FIG. 7 is a fragmentary detailed view in section as taken on the line 7-7 of FIG. 4 and on an enlarged scale; and

FIG. 8 is a schematic diagram showing the sensing means and the hoist controlling means.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there is shown hoisting apparatus for positioning a tong assembly T vertically with respect to a string of well pipe, such as well drilling pipe P having a joint J which interconnects the pipe stands. The hoist apparatus includes a vertically disposed column 10 formed, in the illustrative embodiment, of an I-beam having a lower or base support 14, and an upper brace or support 12 is connected to the top of the column 10. Upper bearing means 16 and lower bearings means 18 provide a pivotal connection for the beam so that it can be rotated on a vertical axis and to enable the tong assembly T to be swung to and from a position aligned with the well bore.

A generally hollow and elongated rectangular support collar 20 is slideably disposed about the column 10 and is adapted to be moved upwardly and downwardly on the column 10. The collar 20 is supported for vertical movement on the column 10 by roller assemblies 22 incorporated within the collar 20. As shown, a plurality of flanged rollers 23 are included in each roller assembly 22 and are engageable with the inner faces of the flanges of the l-beam column to maintain the collar against cocking on the column.

A tong supporting yoke structure 24 is mounted on the collar 20 and projects horizontally therefrom, the yoke structure 24 supporting the pipe tong assembly T. This tong assembly, as is cutomary, includes a backup tong 26 and a power driven tong 30 interconnected together and mounted within a cradle assembly 32. An example of a power tong assembly T of the type generally disclosed herein is more particularly shown and described in the application for US. letters patent Ser. No. 134,552, filed Apr. 16, 1972, in the name of Carl A. Wilms, and assigned to the parent corporation of the wholly owned subsidiary corporation to which the present application is assigned. in such an assembly, the backup tong 26 is adapted to hold one section of a joint .I in the pipe P against rotation while the power driven tong 30 engages the other joint section and rotates the same in a selected direction depending upon whether the joint is being made up or broken out.

Disposed adjacent to and extending vertically along side the column 10 is a power source 34 shown in the form of a hydraulic piston and cylinder actuator unit. The power source 34 is pivotally mounted at its lower end to the lower support 14 and has at its upper end a roller or sprocket 38 over which one or more roller chains 36 extend, the chains 36 being anchored at their lower ends to the lower support 14 and extending upwardly over the sprocket 38 to provide a downwardly extending run which is connected to the yoke structure 24. The arrangement of the hoist chain and piston cylinder unit is such that the movement of the tong assembly T is twice the movement of the power source so that the tong can be moved over a large vertical span with out necessitating an equally long actuator.

In the use of the tong hoist when running the pipe string P, the tong is lowered to a location affording clearance for the pipe supporting elevator until the pipe in the well bore is supported by the usual slip mechanism and the elevator is released. A next stand of pipe is then stabbed into the upper end of the pipe string and the tong assembly T is elevated to a location at which the respective tongs are engageable with the tool joints. When retrieving or pulling the pipe string, the tong assembly T is also lowered to enable the elevator to be latched on or lowered onto the pipe string supported in the slips, and when successive joints are raised the tong assembly T is elevated by its hoist to enable the tongs to engage the tool joints, as more specifically described below.

The present invention is addressed to the problem of positioning the tong assembly T with respect to the pipe P so that the pipe gripping mechanism or jaws within the respective backup tong and

power tong

26 and 30, as shown in broken lines in FIG. 2 and designated 26a and 30a, are adapted to engage the respective joint sections 26b and 30b of the pipe joint J, not only when the pipe string P is being pulled from the well, but also when the pipe string is being run back into the well. During the removal of the pipe string from the well, the tool joints in the pipe string must be broken out, and during running of the pipe string the joints in the pipe string must be made up. During the running in and retrieving of the pipe string from the well, it is, as pointed out above, hoisted or lowered in an elevator adapted to be hoisted by the usual drilling rig draw works, and the pipe string in the well is supported in the usual slip mechanism, while a length or stand of pipe is being broken out of or being made up in the pipe string. During the period that the pipe string is not supported in the slips but is being moved by the elevator, the tong assembly T is normally lowered to an out-of-the-way location, but when the pipe string is supported in the slips the tong assembly T must be elevated to a position at which the

pipe gripping jaws

26a and 30a are adapted to engage the tool joint sections 26b and 30b. Proper positioning of the tong assembly T with respect to the pipe 1 is difficult, at best, but the difficulty is increased when visibility is poor such as at night or during inclement weather.

Accordingly, the present invention involves the utilization of pipe joint detecting means M located between the backup tong 26 and power tong 30 so as to scan the pipe as the tong assembly T is being elevated and detect a joint so as to cause the hoist mechanism to be deenergized when the tong assembly T is at its proper location.

As seen in FIG. 7 the joint detector means M is a magnetic eddy current detector device, such as the model ED-400 MAGNATEST instrument of Magnaflex Corporation, referred to above, incorporated in an assembly whereby the device is adapted to closely fol low the pipe joint sections.

More particularly, the instrument M includes an elongated hollow case suitably mounted on the backup tong assembly 26 as by releasable clamps or brackets 101, so that the overall disposition of the case 100 on the tong 26 can be adjusted radially with respect to the pipe opening 102 through the tong assembly.,Other modes of supporting the case 100 may be employed, including, if desired, means for retracting the case when the sensor is not in use and moving the case to an opperative position.

Within the outer case or body 100 of the instrument M is an inner elongated body 103 having a cylindrical outer surface 104 on which is longitudinally and slidably disposed a sleeve 105. interposed between

opposed shoulders

106 and 107 on the inner body 103 and the sleeve 105, respectively, is a coiled compression spring 108 which normally biases the sleeve outwardly with respect to the case 100. The sleeve 105 is maintained in a predetermined orientation within the case 100 by means of a suitable fixed pin 109 and pin receiving elongated slot 1 10 in the sleeve 105. Suitably affixed to the outer end of the sleeve 105 is a sensing head 111, this head 111 rotatably supporting a pair of vertically and laterally spaced

rollers

112 and 113 on axles 1 14, whereby the proximity of the head 11 l to the pipe P and more particularly to the joint sections 26b and 30b is pre-determined, the spring 106 maintaining a bias on the sleeve 105 which causes the sleeve to be projected longitudinally from the case 100 to an extent limited by the length of the slot 110. The length of the slot may be such that the outward extension of the sleeve 105 with respect to the case 100 is so limited that the

rollers

112 and 113 may not contact the reduced diameter or mid-section of the pipe P, but in any event the enlarged diameter coupling portions or tool joints 26b and 30b are engageably by the

rollers

112 and 113, notwithstanding variations in the diameter of the tool joints which may be caused by wear.

Carried by the head 11 1 and extending telescopically into a bore 115 within the inner body 103 is a tubular support 116 which is adjustably threaded at 117 into the head 11] and contains a coil assembly 118 encapsulated within insulating body 119 and including coils Cl and C2 connected by

conductors

120 and 121 respectively to the current inducing and detecting system hereinafter to be described, whereby the anomaly at the upper end shoulder 1220 of the lower tool joint box 122 which is engageable with the anomaly at the downwardly facing shoulder 124a on the pin end 124 of the upper pipe section causes a variation in the eddy current in the tool joint, whereby to establish a signal for interrupting operation of the hoist power means 34 when the tong assembly T is in the proper relationship to the tool joint as shown in FIG. 4, at which position, as seen in FIG. 2, the

jaws

26a and 30a of the backup tong and

power tong

26 and 30 respectively are engageable with the tool joints 26b and 30b.

The coils C1 and C2 are in circuit with the control means, as typical of the ED-400 MAGNATEST instrument referred to above. Referring to FIG. 8 it will be noted that the coils C1 and C2 are connected to a bridge circuit 130 containing the usual fixed and variable balancing resistances and connected to a power source 131. The output signal from the bridge circuit 130 is supplied to a tuned pre-amplifier 132, the output of which is supplied to an amplifier 133 which is adjustable by sensitivity control potentiometer means 134. The output from the amplifier 133 drives a demodulator 135 to produce an output signal which is supplied to a meter 136. In addition, the undemodulated signal from the amplifier 133 is supplied to a threshold switch 137 containing a silicon rectifier which is adapted to be triggered when the undemodulated signal is at a predetermined level as, determined by a threshold switch adjustor potentiometer 138. When the threshold switch 137 is triggered, a relay 139 is energized to control operation of the hoist power source 34, and if is desired, a glow tube 140 may be in circuit with the relay 139 to indicate that it has been energized.

As also seen in FIG. 8, the hoist means 34 is adapted to be elevated by hydraulic fluid pressure supplied to a cylinder 34a beneath the piston 34b, under the control of a combined manual and automatically operated valving system. The valving system includes a pilot operated main valve MV which is, for illustrative purposes, normally spring loaded to a position at which fluid pressure supplied from a supply conduit 141 is shut off from the actuator cylinder 34a and flows to tank at 142. At the same time pilot fluid pressure is exhausted to tank at 143 through a normally closed throttle valve TV via the

pilot conduits

144 and 145, as shown in broken lines, and pilot pressure from a source conduit 146 is shut off at the valve TV.

When it is desired to exhaust pressure fluid from the actuator cylinder 34a the valve TV is shifted left, as seen in F l6. 8 to establish communication between the pilot pressure source 146 and the pilot conduit 144 so as to shift the main valve MV to the left as viewed in FIG. 8, whereby fluid pressure from the source 141 is supplied via a conduit 147 to a nonnally closed pilot valve 148 to open the latter and allow fluid to exhaust from the actuator cylinder 34a through the conduit 149 and thence to the tank at 142 through the main valve MV. When it is desired to elevate the tong assembly T by applying fluid under pressure to the actuator cylinder 34a, the throttle valve TV is shifted to the right, thereby applying pilot fluid pressure to the main valve and thereby shift it to the right to establish communication between the source conduit 141 and the conduit 149 leading to a back flow preventing valve 1490 bypassing the pilot valve 148, which will effect elevation of the tong assembly T and hold it in the elevated position.

The main valve MV is also shiftable between its two positions from its center position by solenoid actuators under the control of a switching circuit generally denoted at 150 and including a down switching mechanism 151 and up switching mechanism 152. The down switching mechanism includes a down relay 153 which is adapted to be energized by a manual switch 154 so as to be latched in the energized condition by a holding switch 153h, so that contacts 155 are maintained to energize the solenoid 155a and move the main valve MV to the left as seen in FIG. 8. correspondingly, the up switching mechanism 152 includes an up relay 156 adapted to be energized by a manual switch 157 which closes holding contacts 158 to maintain contacts 159 closed and energize the solenoid 159a of the main valve MV. Each of the down and up switching

mechanisms

151 and 152 also includes a manual switch 15512 and 15%, respectively adapted to manually energize the

respective solenoids

155a and 159a in an overriding man ner. interposed in the circuit with the down and up

relays

153 and 156 are respective switches 153a and 156a which may be suitably actuated to an open position to limit upward and downward motion of the tong assembly beyond a fixed range when the system is being controlled by the eddy current detector means M. Now it will be apparent that energization of the up and down switching

circuitry

151 and 152 requires that the contacts 1390 of the control relay 139 be closed to complete the circuit between a source conductor [39b and one side of the

respective relays

153 and 156. If desired, the detector operated relay 139 or some other signal responsive means which is energized when the joint J is properly positioned in the tong assembly T, may be operated to effect actuation of the tongs 26 and What is claimed is:

1. In combination, pipe tong means engageable with the threadedly engaged joint portions of a tool joint of well pipe extending vertically into a well bore for making up and breaking out said tool joint portions, power actuated hoist means associated with said pipe tong means for vertically moving said pipe tong means along the well pipe between a first inoperative position in which said pipe tong means is below the tool joint and a second inoperative position in which said pipe tong means is above the tool joint, control means associated with said hoist means for controlling the movements of said pipe tong means between said positions, said control means including magnetic eddy current responsive detector means carried by said pipe tong means and sensitive to the tool joint for operating said control means to stop said hoist means when said pipe tong means moves into operative position adjacent to the tool joint in which position said pipe tong means is engageable with the joint portions, and wherein said detector means has a sensing head provided with spacing means for predetermining the space between said sensing head and said joint portions.

2. In combination, pipe tong means engageable with the threadedly engaged joint portions of a tool joint of well pipe extending vertically into a well bore for making up and breaking out said tool joint portions, power actuated hoist means associated with said pipe tong means for vertically moving said pipe tong means along the well pipe between a first inoperative position in which said pipe tong means is below the tool joint and a second inoperative position in which said pipe tong means is above the tool joint, control means associated with said hoist means for controlling the movements of said pipe tong means between said positions, said control means including magnetic eddy current responsive detector means carried by said pipe tong means and sensitive to the tool joint for operating said control means to stop said hoist means when said pipe tong means moves into operative position adjacent to the tool joint in which position said pipe tong means is engageable with the joint portions, and wherein said detector means has a sensing head provided with spacing means for predetermining the space between said sensing head and said joint portions, said spacing means comprising vertically and laterally spaced joint portion engaging elements adapted to bridge the anomoly at said joint portions.

3. in combination, pipe tong means engageable with the threadedly engaged joint portions of a tool joint of well pipe extending vertically into a well bore for making up and breaking out said tool joint portions, power actuated hoist means associated with said pipe tong means for vertically moving said pipe tong means along the well pipe between a first inoperative position in which said pipe tong means is below the tool joint and a second inoperative position in which said pipe tong means is above the tool joint, control means associated with said hoist means for controlling the movements of said pipe tong means between said positions, said control means including magnetic eddy current responsive detector means carried by said pipe tong means and sensitive to the tool joint for operating said control means to stop said hoist means when said pipe tong means moves into operative position adjacent to the tool joint in which position said pipe tong means is engageable with the joint portions, and wherein said detector means includes a sensing head having a coil assembly, means supporting said sensing head for movement towards said joint portions, biasing means for urging said sensing head towards said joint portions, and means for positioning said coil assembly in spaced relation to said joint portions.

4. In combination, pipe tong means engageable with the threadedly engaged joint portions of a tool joint of well pipe extending vertically into a well bore for making up and breaking out said tool joint portions, power actuated hoist means associated with said pipe tong means for vertically moving said pipe tong means along the well pipe between a first inoperative position in which said pipe tong means is below the tool joint and a second inoperative position in which said pipe tong means is above the tool joint, control means associated with said hoist means for controlling the movements of said pipe tong means between said positions, said control means including magnetic eddy current responsive detector means carried by said pipe tong means and sensitive to the tool joint for operating said control means to stop said hoist means when said pipe tong means moves into operative position adjacent to the tool joint in which position said pipe tong means is engageable with the joint portions, and wherein said detector means includes a sensing head having a coil assembly, means supporting said sensing head for movement towards said joint portions, biasing means for urging said sensing head towards said joint portions, and means for positioning said coil assembly in spaced relation to said joint portions including spacer means carried by said sensing head and engageable with said joint portions.

5. In combination, pipe tong means engageable with the threadedly engaged joint portions of a tool joint of well pipe extending vertically into a well bore for making up and breaking out said tool joint portions, power actuated hoist means associated with said pipe tong means for vertically moving said pipe tong means along the well pipe between a first inoperative position in which said pipe tong means is below the tool joint and a second inoperative position in which said pipe tong means is above the tool joint, control means associated with said hoist means for controlling the movements of said pipe tong means between said positions, said control means including magnetic eddy current responsive detector means carried by said pipe tong means and sensitive to the tool joint for operating said control means to stop said hoist means when said pipe tong means moves into operative position adjacent to the tool joint in which position said pipe tong means is engageable with the joint portions, and wherein said detector means includes a sensing head having a coil assembly, means supporting said sensing head for movement towards said joint portions, biasing means for urging said sensing head towards said joint portions, and means for positioning said coil assembly in spaced relation to said joint portions including spacer means carried by said sensing head and engageable with said joint portions at vertically and laterally spaced locations.

6. in combination, pipe tong means engageable with the threadedly engaged joint portions of a tool joint of well pipe extending vertically into a well bore for making up and breaking out said tool joint portions, power actuated hoist means associated with said pipe tong means for vertically moving said pipe tong means along the well pipe between a first inoperative position in which said pipe tong means is below the tool joint and a second inoperative position in which said pipe tong means is above the tool joint, control means associated with said hoist means for controlling the movements of said pipe tong means between said positions, said control means including magnetic eddy current responsive detector means carried by said pipe tong means and sensitive to the tool joint for operating said control means to stop said hoist means when said pipe tong means moves into operative position adjacent to the tool joint in which position said pipe tong means is engageable with the joint portions, and wherein said detector means includes a sensing head having a coil assembly, means supporting said sensing head for movement towards said joint portions, biasing means for urging said sensing head towards said joint portions, and means for positioning said coil assembly in spaced relation to said joint portions including means adjustably supporting said head on said detector means.

7. In combination, pipe tong means engageable with the threadedly engaged joint portions of a tool joint of well pipe extending vertically into a well bore for making up and breaking out said tool joint portions, power actuated hoist means associated with said pipe tong means for vertically moving said pipe tong means along the well pipe between a first inoperative position in which said pipe tong means is below the tool joint and a second inoperative position in which said pipe tong means is above the tool joint, control means associated with said hoist means for controlling the movements of said pipe tong means between said positions, said control means including magnetic eddy current responsive detector means carried by said pipe tong means and sensitive to the tool joint for operating said control means to stop said hoist means when said pipe tong means moves into operative position adjacent to the tool joint in which position said pipe tong means is engageable with the joint portions, and wherein said detector means includes a sensing head having a coil assembly, means supporting said sensing head for movement towards said joint portions, biasing means for urging said sensing head towards said joint portions, and means for positioning said coil assembly in spaced relation to said joint portions including means adjustably supporting said head on said detector means, and spacer means carried by said sensing head and engageable with said joint portions.

8. The combination of claim 1, wherein said hoist means includes actuator means, means for supplying motive power to said actuator means, and said control means including manually operable means for controlling the application of motive power to said actuator means.

9. The combination of claim 1, wherein said hoist means includes a fluid pressure operated actuator for raising said tong means, said control means including valve means shiftable between selected positions for controlling the application of pressure fluid to and the exhaust of pressure fluid from said actuator, and means responsive to said detector means for shifting said valve means to the position for the application of pressure fluid to said actuator.

10. The combination of claim 1, wherein said hoist means includes a fluid pressure operated actuator for raising said tong means, said control means including valve means shiftable between selected positions for controlling the application of pressure fluid to and the exhaust of pressure fluid from said actuator, and means responsive to said detector means for shifting said valve means to the position for the application of pressure fluid to said actuator, and also including means responsive to said detector means for shifting said valve means to the position for the exhaust of pressure fluid from said actuator.

11. The combination of claim 1, wherein said hoist means includes a fluid pressure operated actuator for raising said tong means, said control means including valve means shiftable between selected positions for controlling the application of pressure fluid to and the exhaust of pressure fluid from said actuator, and means responsive to said detector means for shifting said valve means to the position for the application of pressure fluid to said actuator, and also including means responsive to said detector means for shifting said valve means to the position for and the exhaust of pressure fluid from said actuator, and manual means for effecting movement of said valve means to said positions.

12.. The combination of claim 1, wherein said hoist means includes a fluid pressure operated actuator for raising said tong means, said control means including valve means shiftable between selected positions for controlling the application of pressure fluid to and the exhaust of pressure fluid form said actuator, and means responsive to said detector means for shifting said valve means to the position for the application of pressure fluid to said actuator, and also including means responsive to said detector means for shifting said valve means to the position for and the exhaust of pressure fluid from said actuator, and manual means for effecting movement of said valve means to said positions, said manual means being incorporated in said means responsive to said detector means.

13. The combination of claim 1, wherein said hoist means includes a fluid pressure operated actuator for raising said tong means, said control means including valve means shiftable between selected positions for controlling the application of pressure fluid to and the exhaust of pressure fluid from said actuator, and means responsive to said detector means for shifting said valve means to the position for the application of pressure fluid to said actuator, and also including means responsive to said detector means for shifting said valve means to the position for and the exhaust of pressure fluid from said actuator, and manual means for effecting movement of said valve means to said positions, said manual means including pilot valve means for positioning the first mentioned valve means.

Claims

12. The combination of claim 1, wherein said hoist means includes a fluid pressure operated actuator for raising said tong means, said control means including valve means shiftable between selected positions for controlling the application of pressure fluid to and the exhaust of pressure fluid form said actuator, and means responsive to said detector means for shifting said valve means to the position for the application of pressure fluid to said actuator, and also including means responsive to said detector means for shifting said valve means to the position for and the exhaust of pressure fluid from said actuator, and manual means for effecting movement of said valve means to said positions, said manual means being incorporated in said means responsive to said detector means.