US2124692A - Casing hook - Google Patents

Description

July 26, 1938- G. F. FERMIER ET AL CASING HOOK Filed June 20, 1956 3 Sheets-Sheet l gmc/wim. ermz'e/T 5t a/r es July 26, 1938. G. F. FERMIER ET AL CAS ING HOOK Filed June 20, 1936 5 Sheets-Sheet 2 U0 m, u.,

Il/IIIIIIIIIIIII lill YIIIIIII A July 26, 1938. G. F. FERMIER ET AL CASING HOOK Filed June 20, 1936 3 Sheets-Sheet 3 4a g 97 -s -95 II., lag@ atenter `luly' 26, 19358 UNITED STATES PATENT OFFICE CASIN G HOOK Application June 20, 1936, Serial No. 86,255

18 Claims.

This invention relates to that type of hooks customarily employed in the construction and operation of oil and gas wells for supporting the casing or drill pipe employed during the drilling operation.

This invention has to do particularly with a resilient hook which will effectively support the weight of a portion of a drill pipe being unscrewed and which will lift such portion away from the part from which it is disconnected as soon as the threads are disengaged.

Hooks of this type are commonly used in putting in or pulling well casings o1' drill stems, to support a section of the casing while it is being unscrewed from the other sections. The separation of the sections is effected by rotating the casing or drill stem at a point below the joint to be broken by means of a rotary table while the section above the joint is held stationary by suitable tongs, or by holding stationary the casing or drill stem at a point below the joint to be broken while the section above the joint is rotated by means of tongs.

In either procedure some means is provided to take up the weight of the upper section during the breaking of the joint, because unless this is done, the weight of the section rests on the screw threads of the joint and tends to grind off and damage the threads. To obviate this damage to the screw threads, and for the purpose of saving time, it is common to support the section being removed by a casing hook provided with a compression spring of such strength as to support the section during the breaking out of the taperthreaded joint, and later after disengagement of the threads to automatically lift said section high enough to free it from all interference with its former mating member.

Where such hooks are provided With merely a spring for lifting the pipe section once it has been disconnected, it has frequently been experienced that an operator is unable to push the section removed aside exactly the moment it is pulled upwardly by the spring, and that on the recoil the section removed will come back 'down and frequently hit against the joint from which it has just been disconnected. This is obviously detrimental tothe threads of the joint and causes considerable damage and delay when it occurs. Furthermore, it is not an unknown occurrence for a workmans hand to slip between the sections when the section is rst lifted, and to be greatly injured when the sections come together again on the recoil.

It is the purpose of this invention to provide a casing hook in which the recoil referred to will be eliminated.

It is a further object of this invention to provide a casing hook which will serve to quickly remove the section from the joint from which it is disconnected, but which will retard any tendency toward recoil and prevent the two parts of the joint from being hammered together once they have been separated by the spring of the casing hook.

With the foregoing and other objects in view, this invention contemplates the various parts and combinations, and the various modifications thereof illustrated in the accompanying drawings.

It is to be understood, however, that while several modications have been illustrated, the same are by way of example only, and it is not to be implied that all possible forms have been shown. It is apparent that various other modifications may be made within the spirit and scope of this invention, such spirit and scope being limited only by the prior art and by the terms of the appended claims.

Referring now more particularly to the drawings in which like numerals indicate corresponding parts throughout;

Fig. 1 is a view partly in vertical cross section illustrating one embodiment of this invention.

Fig. 2 is a horizontal section taken along the line 2 2 of Fig. 1, and illustrating the adjusting 30 means employed in connection with the form shown in Fig. 1.

Figs. 3 to 8, inclusive, are views similar to Fig. 1, but illustrating various modied arrangements of the respective parts.

Figs. 1a, 4a and 8a are enlarged fractional portions of Figs. 1, 4 and 8, respectively.

Fig. 9 is a View illustrating the application of a casing hook constructed in accordance with this invention. 5

Referring rst to the form shown in Fig. 1, the hook l is supported by means of a yoke 2 or the like, such yoke having eyelets 3 at its lower ends adapted to be received on the pintles 4 of the block 5. The eyelets 3 are held on the pintles 4 45 by means of cap screws 6 or the like which secure the washers 1 in place.

The block 5 is provided with a central bore having a reduced portion at its upper end within the externally threaded extension 8 of the block 5. 50 Threaded onto this extension 8 is a tubular member or cylinder 9 which extends upwardly from the block. A passageway l0 constituting a bypass is formed through the extension 8 in a longitudinal direction and communicates with the inte- 55 CII rior of the tubing 9 and with the interior of the lower portion of the bore through the block 5. The'size of this passageway I0 may be regulated by suitable means such as a screw valve II. A second passageway I0', spaced from the passageway I0, also extends between the interior of the tubing 9 and with the interior of the lower portion of the bore through the block 5. This passageway III is controlled by a ball valve I I which permits free movement therethrough in an upward direction but prevents movement therethrough in a downward direction.

The hook has a portion fitting within the lower part of the boreA in the block 5 and provided with a cup-shaped Washer I2 so as to form a fluid seal between this portion of the hook and the walls of the bore in the block. Thewalls I3 of this bore are machined smooth so that the packing or washer I2 may slide therein with the least possible friction and form a good seal. Above the washer I2 the hook I carries a stem I4 of reduced size, and the upper end of this stem is threaded at I5 to receive a nut I6 forming a plunger which rides up-and down within the cylinder 9. At a point adjacent its lower end this plunger is provided with a cup-shaped washer I1 similar to the washer I2 on the lower portion of the hook with the exception that the washer I1 is inverted. The upper end of the nut I6 is provided with a head which extends laterally and limits the downward movement not only of the nut I6, but of the hook I as well. This nut I6 is locked in place by means of a lock nut I9.

Positioned below the lower end of the nut I6 and seated on the upper end of the extension 8 of the block 5 is a compression spring 20 which is adapted to support the weight as hereinbefore referred to. A plug or other means may be provided adjacent the upper end of the cylinder 9 for the purpose of atl least partially filling this cylinder and the lower portion'of the bore through the block 5 with a suitable liquid, which liquid will act with a dashpot effect when the hook is operated as will now be described.

The hook I is connected to a section of pipe and an upward pull exerted until the spring 20 is compressed to the extent that the force exerted by the spring will be suicient to raise the section of pipe as soon as it is disconnected. When the section is disconnected, the force of the spring will cause the pipe to be raised quickly, the fluid passing freely upwardly through passageway I0', until the joint at the lower end of the pipe is free from the joint to which it has just been disconnected. The dashpot eiect of the fluid now comes into play, the valve Il closing and the fluid on its downward movement being forced past the metering screw II. This prevents any rapid downward movement of the hook, and consequently of the pipe section which has just been removed. This dashpot arrangement thereby takes up the recoil which would ordinarily be taken up by the spring itself, and prevents the downward recoil movement which has been referred to above.

In the form illustrated in Fig. 3, the hook 2l is supported by the yoke 22, the lower ends of which are formed with eyelets 23 engaging the lugs 24 in a manner very similar to that illustrated in Fig. 1. The lugs 24 are carried on a block 25 which is for the most part hollow and open at its upper end, but which is provided with an upstanding cylindrical portion 26 centrally thereof. The cylindrical portion 26 when taken with the outer walls of the block 25 provide an inner cylindrical chamber 21 and an outer annular chamber 28. Passing through the inner chamber is the stem 29 which is integral with the upper end of the hook 2|, and surrounding this stem 29 is the compression spring 30 corresponding to the spring 29 of Fig. 1. The stem 29 is threaded at its upper e'nd as at 3| to receive an inverted cup-shaped plunger member 32. This member 32 has downwardly extending walls 33 carryingv at their lower ends an annular plunger 34 which is of such a size as to fit fairly snugly within the annular chamber 28. This plunger 34 is .provided with a by-pass 35 extending from its upper to its lower surface. In addition to the bypass 35 through the plunger 34, the block 25 is also provided with two or more by-passes. One of these by-passes 36 is normally closed to prevent movement of the fluid therethrough from the space below the plunger to the space above the same by means of a check valve 31. The check valve 31, however, is arranged to permit free movement of the fluid from the space above the plunger to the space below the same. The other by-pass 38 is likewise provided with a check valve 39, this check valve being spring pressed by a spring 40 to retard movement of fluid from below the plunger to the space above the same, and to positively prevent movement of fluid from the space above the plunger to the space below the same. ,Y

The upper end of the block 25 is preferably closed by a plate or dome 4I secured in place by means of cap screws or the like 42.

In this form, the operation is similar to that illustrated in Fig. 1 with the exception that upon upward movement of the hook 2I the fluid is permitted to pass freely through the by-pass 36 in the block 25 and thus permit the upward movement of the hook to be swift and sudden. On the other hand, the downward movement is limited both by the size of the opening 35 and by the strength of the spring 40 so that the recoil which it is desired to eliminate will be effectively damped.

With reference to the form illustrated in Fig. 4, this is very similar to that shown in Fig. 3. In this form the hook 43 is supported by the yoke 44 having the eyelets 45 in engagement with the lugs 46- on the block 41. An upstanding cylindrical wall 48 is provided within this block 41, the same being very similar to the wall 26 in Fig. 3. Passing through the chamber 49 within this cylindrical wall 48 is the stem 5I on the hook 43 and the spring 52 surrounds this stem in precisely the same manner as shown in Fig. 3. Secured to the threaded upper end 53 of the stem 5I is the plunger member 54 which has downwardly extending walls 55 carrying the annular plunger 56. In this instance, the annular plunger is so formed as to fit the annular chamber 50 loosely. 'I'he plunger is provided with a bypass opening 51 therethrough similar to the opening 35 of Fig. 3. On the lower surface of this annular plunger there is mounted a U-shaped packing Washer 58 secured in place by means of a ring 59 held to the plunger by cap screws 60 or the like. The upper end of the block 41 is closed by a plate or dome 6I held to the block by screws 62 in the manner readily apparent.

The operation of this hook is likewise similar to that shown in Fig. 3, the exception being that upon upward movement of the hook the uid is allowed to pass from above the piston to the space below the piston by virtue of the shape of the cup-shaped packing 58, the by- passes 36 and 36 in the block being omitted.

In the form shown in Fig. a somewhat diierent arrangement is provided. 'I'he hook 63 in this instance is supported by a yoke 64 having eyelets 65 mounted on the lugs 66 of the block 61`.

. The block 61, however, is provided with two cy- QJI lindrical chambers therein 68 and 69, these chambers being connected at their lower ends by a passageway 10. 'I'here is also a passageway 1| which connects the upper en'ds of these cylindrical chambers, and which passes adjacent the lower end of the cylindrical chambers and adjacent the passageway 10. 'I'he passageways 10 and 1| are interconnected by means of arestricted opening 12, and also by means of an opening 13 controlled by a ball Valve 14 normally urged into seated position by a spring 15. The lower ends of the chambers 60 and 69 are also connected to the passageway 1|, these connections being controlled by the ball valves 16 and 11, respectively, so positioned as to permit passage of fluid from the passageway 1| into the respective chambers, but to prevent such passage in the opposite direction. The balls 16 and 11 are retained adjacent the openings they control by means of guards 10 and 19.

The upper ends of the chambers 00 and 99 are closed by means of plugs 80 and 8|, respectively, threaded into the upper ends of the chambers. Each of these plugs is provided with an opening through which the piston rods 32 and 83 are adapted to move. These piston rods carry the pistons 84 and 85, respectively, and are connected at their upper ends by means of a cross head 90. The cross head 86 is secured to the upper end of the stem of the hook by means of a nut 0l' or the like, the connection being loose so that the hook may swivel with respect to the plungers. The hook in this instance extends upwardly through the block, and is provided with a compression spring surrounding its stem in substantially the same manner as illustrated in Fig. 7 of the drawings.

In operation, the device of Fig. 5 permits rapid movement of the hook upwardly, the fluid within the cylindrical chambers 60 and 69 passing in such instance from the space above the pistons through the passageway 1| and into the space below the pistons through the valves 16 and 11. 0n downward movement, however, the hook is forced to move slowly by the dashpot eifect created by the necessity for the fluid in moving from below the pistons to above the same to pass through the restricted opening 12, and through the passageway 13 controlled by the spring pressed valve 14.

in Fig. 6, the hook 88 is supported by a yoke 89 having eyelets 90 engaging the plugs 9| on the block 92 in substantially the same manner as hereinbefore described. The block 92, however, is in this instance formed with a single cylindrical chamber 93 and with a passageway 94 connecting the upper end of this chamber with the lower end thereof. Adjacent the lower end of the chamber this passageway 94 communicates with the interior of the chamber through a restricted openingV 95, and at its lower end this passageway is controlled by a valve 96 retained in place by a guard 91. As will be seen,l this valve is such as to permit free passage of fluid into the lower end of the chamber, but to prevent passage from the lower end of the chamber except through the restricted opening 95.

The upper end of the cylindrical chamber 93 is closed by a threaded plug 98 having an opening therethrough receiving the slidable piston rod 99. On its lower end this piston rod carries the piston |00 which is reciprocable in the cylindrical chamber and secured at its upper end is the cross head |0|. 'I'his cross head |0| is secured to the stem of the hook 88 by a nut |02 or the like, these connections and the spring which surrounds the stem of the hook within the block 92 being substantially the same as that illustrated in Fig. '1 now to be described.

It will be appreciated that in this form the hook 88 is permitted to move upwardly without restriction, the uid which is employed within the cylinder 93 passing in such instance from the upper portion of the cylinder to the lower portion of the cylinder through the valve 96. On its downward movement, however, it is restricted to passage through the small opening 95 and the recoil is thus substantially eliminated.

In Fig. '7, the arrangement is substantially the same as in Fig. 6, the hook |03 being supported by a yoke |00 which is in turn secured to the block |05 in substantially the same manner. The block |05 is similar provided with a single cylindrical chamber |00 and with a passageway |01 connecting the upper portion thereof with the lower portion thereof. rl'he lower end of this passageway communicates with the interior of the chamber |06 through two openings, one of which is controlled by a spring pressed valve |00 held in place by a spring |09, and the other oi which is controlled by a call valve ||0 retained by a guard iii. The upper end of the chamber is closed by a plug ||2 formed to accommodate the piston rod ili carrying a piston lill at its lower end. At its upper end a cross head H5 is provided. By means of a castle nut H0, the cross head iliiis secured to a fitting M0 in such a manner as to permit the fitting to swivel with respect to the cross head. This itting is in turn threaded at liti to the upper end of the stem |20 on the hook |03. Surrounding the stem |20 between the lower portion of the block |05 and the fitting H0 is a compression spring |2i, this spring having the same function as the springs illustrated in Figs. i, 3 and In this form of hook, upward movement of the hook is permitted freely by virtue of the fact that the fluid which is used within the cylindrical chamber |06 may pass from above the piston through the passageway |01 and upwardly into the space below the piston through the valve I0. On downward movement, however, the fluid must pass by the spring pressed valve |00, the strength of the spring |09 being such as to damp the movement of the piston by restricting the movement of the fluid from below the piston.

In the illustration of Fig. S, the hook |22 is supported by the yoke |23 having eyelets |24 on its lower ends engaging the plugs |25 on the block |26. The block |26 has a cylindrical chamber therein at |21, but is not provided with any passageways corresponding to those described in the preceding paragraphs. The upper end of the chamber |21 is closed by a plug |28 which is formed to provide for the passage of the piston rod |29. The piston |30 is carried on the lower end of this rod and fits loosely within the chamber |21. A cup-shaped packing |3| is secured to the lower face of the piston' |30 by means of a plate |32 and cap screws or the like |33. Extending through the piston |30, the packing |3|, and the plate |32, is a passageway |34 of such i pipe.

size as to restrict the passage of fluid therethrough.

The upper end of the piston rod |29 is secured to a cross head |35 which is in turn secured to the upper end of the stem or hook |22 by means of a nut |36 or the like. The connection between the hook |22 and the nut |36 is similar in all respects to the corresponding structure shown in Fig. 7.

In this form, the upward movement of the hook |22 is unrestricted because of the fact that the fluid which is used in the chamber |21 may pass unrestrictedly by the piston |30 and the cup-shaped packing |3|. On downward movement, however, the fluid is held by the packing |3| and is compelled to pass through the restricted passageway |34 in moving from below the piston to the space above the same. Any recoil is thereby taken up.

The application of the various casing hooks above described is illustrated in Fig. 9, the hook of Fig. 3 being shown here for purposes of illustration. It will be seen that the hook 2| in this instance is engaged with a yoke |31 secured to a clamp |38 by which the section of tubing |39 is being held. On the lower end of this section of tubing is the pin portion of a tool joint |40, the box portion |4| being on the upper end of the string of pipe |42. This string is in this instance supported by means of slips |43 carried by a suitably supported block |44 in a manner which is well known to those skilled in the art. When it is desired to disconnect a section such as |39, the section is pulled to a point above the support |44 and the slips |43 are then engaged to support the lower portion of the string of A sufficient force is exerted on the hook 2l to compress the spring 30 included therein, and to move the annular piston 34 to its lowermost position. The tool joint sections |40 and |4| are thereupon unscrewed to disjoint the section |39. Immediately upon disengagement of the threads of the respective parts of the tool joint the spring 30 will expand andcause the annular piston 34 to be raised to its uppermost position within the annular chamber 28. In such .movement fluid is permitted to pass from above the piston through the passageway 36 and pass the Valve 31, no restriction being imposed upon this passage of fluid. This leaves the section |39 in the position illustrated in Fig. 9. Naturally, there is a. tendency for a recoil to take place, and for this section to again move downwardly tending to bring the threaded ends of the tool joint into engagement the second time. This is prevented, however, in this instance by virtue of the fact that the iluid is trapped in the annular space below the piston 34, and before this piston can move downwardly, and hence before the hook 2| and the section |39 can move downwardly, the fluid must either pass through the small opening 35 in the piston, or must be forced past the spring pressed valve 39, and through the passageway 30. Since it requires considerable time for the fluid to pass from one space to the other by either of these routes, the tendency to recoil is effectively overcome.

In the foregoing description and in the following claims this invention has been referred to as a casing hook. It will be understood, however, that this term is not intended as in any way a limitation, but that it is intended that this invention shall include all hooks of the nature claimed which are capable of being employed either during the removal of a casing from a well, or during the removal of a drill stem, or during the removal of any other pipe or rod from a well or other opening.

It will also be understood that the term hook is to be taken as including elements notnecessarily shaped as hooks but performing the function of hooks disclosed in this application and that the term "yoke" is likewise to be taken as including elements shaped differently from the yoke elements disclosed in the drawing of this application but performing substantially the same function, namely, the function of a pendant support.

In view of the foregoing, it will be seen that a means has been provided for carrying out all the objects and advantages sought by this invention.

Having described our invention, we claim:

l. In a casing hook, in combination, a yoke member, a spring supported thereby, a hook member supported on said spring, a dashpot having relatively movable parts connected to said yoke and to said hook, respectively, said dashpot including means for retarding without substantially restricting downward movement of said hook while permitting substantially free upward movement thereof with respect to said yoke.

2. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber therein, v

a spring carried by said member, a hook supported on said spring, a piston in said chamber and connected with said hook for movement in said chamber on upward or downward movement of said hook, and means for retarding a flow of fluid past said piston on downward movement of said hook and for conducting such uid freely past said piston on upward movement of said hook, whereby said hook will be retarded on downward movement, and free from retardation on upward movement.

3. In a casing hook, a yoke, a member carried by said yoke and having a liquid chamber therein, a spring carried by said member, a hook supported on said spring, a plunger movable in said chamber and connected with said hook for movement in said chamber on downward movement of said hook, a liquid in said chamber, and means retarding the escape of said liquid from its position in said chamber ahead of said plunger on downward movement of said hook.

4. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber and a spring chamber therein, a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected with said hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, and means retarding the escape of said fluid from its position in said chamber ahead of said plunger upon downward movement of said hook.

5. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber and a spring chamber therein, a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected with said hook for movement in said chamber on downward movement of said hook, a swivel connection between said hook and said plunger, a fluid in said chamber, and means retarding the escape of said fluid from its position in said chamber ahead of said plunger upon downward movement of said hook.

6. In a casing hook, a yoke, a. member carried by si id yoke and having a fluid liamber and a spring chamber therein, said fluid and spring chambers being spaced laterally from each other, a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected with said hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, and means retarding the escape of said fluid from its position in said chamber ahead of said plunger upon downward motion of said hook.

7. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber and a spring chamber therein, said fluid and spring chambers being substantially concentric with respect to each other, a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected with said hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, and means retarding the escape of said fluid from its position in said chamber ahead of said plunger upon downward motion of said hook.

8. In a casing hook, a yoke, a member carried by said yoke, and having a fluid chamber and a spring chamber therein, a spring in said spring chamber, a hook supported on said spring, a piston in said fluid chamber and connected with said hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, means retarding the escape of said fluid from its position ln Ysaid chamber ahead of said plunger upon downward motion o f said hook, and for freely conducting uid into said chamber upon upward motion of said hook.

9. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamberand a spring chamber therein, said fluid and spring chambers being substantially concentric and said fluid chamber being of annular form, a spring in said spring chamber, a hook supported on said spring, an annular plunger in said annular fluid chamber and connected with said hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, and means retarding the escape of said fluid from its position in said chamber ahead of said piston upon downward motion of said hook.

10. In a casing hook, a yoke, a member carried by said yoke and having a liquid chamber therein, a spring carried by said member, a hook supported on said spring, a plunger movable in said chamber and connected with said hook for movement in said chamber on downward movement of said hook, a liquid in said chamber, and means retarding the escape of said liquid from its position in said/chamber ahead of said plunger upon downward motion of said hook and for freely admitting fluid to said chamber upon upward motion of -said hook.

11. In a casing hook, a yoke, a member carried by said yoke and havinga liquid chamber therein, a spring within said liquid chamber, a hook supported on said spring, a plunger movable in said chamber and connected with said hook for movement in said chamber on downward movement of said hook, a liquid in said chamber, and means retarding the escape of said liquid from its position ln said chamber ahead of said plunger upon downward motion of said hook.

12. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber and a spring chamber therein, said fluid and spring chambers being spaced laterally from each other,

a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected to said hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, said chamber having a restricted opening therein for permltting retarded escape of said fluid from its position in said chamber ahead of said plunger upon downward movement of said hook, and a freely operating check valve for freely admitting fluid to said chamber upon upward movement of said hook.

13. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber and a spring chamber therein, said fluid and spring chambers being spaced laterally from each other, a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected with said hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, said chamber having a restricted opening therein for permitting unrestricted escape of said fluid from its position in said chamber ahead of said plunger upon downward movement of said hook, a springpressed check valve arranged to permit additional escape of said fluid upon placing of an excessive load on said hook, and a freely operating check valve for freely admitting fluid into said chamber upon upward movement of said hook.

14. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber and a spring chamber therein, said fluid and spring chambersbeing spaced laterally from each other, a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected with ksaid hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, a flexible cupshaped washer on said plunger for preventing movement of said fluid between the walls of said chamber and the sides of said plunger upon downward movement of said hook, but permitting relatively free movement of said fluid in the opposite direction upon upward movement of said hook, and said plunger having a restricted passageway therethrough for permitting retarded escape of said fluid from its position in said chamber ahead of said plunger upon downward motion of said hook.

15. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber and a spring chamber therein, said fluid and spring chambers being substantially concentric with respect to each other, a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected with said hook for movement in said chamber on downward movement of said hook, a fluid in said chamber, said chamber having a restricted opening therein for permitting retarded escape of said fluid from its position in said chamber ahead of said plunger upon downward movement of said hook, a springpressed check valve arranged to permit additional retarded escape of said fluid upon the placing of an excessive load on said hook, and a freely movable check valve arranged to freely admit fluid to said chamber upon upward movement of said hook.

16. In a casing hook, a yoke, a member carried by said yoke and having a fluid chamber and a spring chamber therein, said fluid and spring chambers being substantially concentric with respect to each other, a spring in said spring chamber, a hook supported on said spring, a plunger in said fluid chamber and connected with said hook for movement in said chamber on downward movement-of said hook, said structure hav.

ing a restricted opening therein for permitting retarded escape of said iluid from its position in said chamber ahead of said plunger upon downward movement of said hook, and a U-shaped washer on said plunger adapted to slidingly contact the walls of said chamber and prevent movement of said fluid past said plunger upon downward movement of said hook while permitting substantially free movement of said uid past said plunger upon upward movement of said hook.

17. In a casing hook, a yoke, a member carried by said yoke and having a spring chamber and a plurality of fluid chambers therein, said fluid chambers occupying balanced positions on oppo-V site sides of said spring chamber, a spring in said spring chamber, a hook supported on said spring, plungers in said fluid chambers respectively, and each connected with said hook for movement in said chambers on downward movement of said hook, a fluid in said chambers, and means retarding the escape of said fluid from its position in said chambers ahead of said plungers upon downward movement of said hook.

18. In a, casing hook, a yoke, a member carried site sides of said spring chamber, a spring in said spring chamber, a hook supported on said spring, plungers in said fluid chambers, respectively, and each connected with said hook for movement in said chambers on downward movement of said hook, a fluid in said chambers, a restricted opening in said chamber for permitting retarded escape of said fluid from its position in said chamber ahead of said plunger upon downward movement of said hook, a spring-pressed check valve arranged to permit additional retarded escape of said fluid from said chamber upon the placing of an excessive load on said hook, and a freely movable check valve arranged to freely admit iluid into said chamber upon upward movement of said hook.

GEORGE F. FERMIER.

JOHN C. STOKES.

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