Locking Apparatus for Locking a Packer Setting Apparatus and Preventing the Packer From Setting Until a Predetermined Annulus Pressure Is Produced

The subject matter of the present invention relates to a locking apparatus for a wellbore packer, and more particularly, to an apparatus adapted to be disposed in a wellbore for locking a setting apparatus to a mandrel, preventing any longitudinal movement of the setting apparatus relative to the mandrel, and preventing a packer connected to the mandrel from being set until a predetermined annulus pressure exists in the annulus section of the wellbore. When the predetermined annulus pressure is reached, the locking apparatus releases the mandrel from the setting apparatus thereby allowing the mandrel to move longitudinally relative to the setting apparatus. Since the packer is connected to the mandrel, any longitudinal movement of the mandrel relative to the setting apparatus will either set or unset the packer depending upon the direction of the longitudinal movement of the mandrel.

When a packer is lowered to a desired depth in a wellbore, it is initially placed in a safety position so that the packer will not set prematurely during its descent into the wellbore. In order to set the packer, it must first be removed from or taken out of its safety position. In order to remove the packer from its safety position, prior art packer setting apparatus required a user to first move a tubing string upwardly and then rotate the tubing string or to move the string up and down without rotation. Such movement of the tubing string can cause disruption of the depth correlation of the packer, as well as other tools, in the wellbore. Furthermore, such movement of the tubing string may accidentally set the packer. For example, since an upward movement followed by a rotational movement of a tubing string would set a prior art packer, the up and down motion of a drilling rig platform may provide the required movement of the tubing string which is necessary to accidentally set the packer. In addition, in deviated or horizontal boreholes, it was often necessary to rotate the tool string many times in order to generate a quarter turn at the packer, the quarter turn being required in order to take the packer out of the safety position. This can cause entanglement of hydraulic hoses used downhole. Accordingly, a new apparatus is needed to lock the packer in a safety position and to easily remove or unlock the packer from its safety position prior to setting the packer. Furthermore, once the packer is unlocked from its safety position downhole and set, any subsequent movement designed to unset the packer will cause the packer setting and unsetting apparatus to revert to standard operation.

Accordingly, it is a primary object of the present invention to provide a locking apparatus adapted for locking a packer in a first condition and for retaining the lock on the packer until a predetermined annulus pressure is reached, the lock being released and the condition of the packer being changed from the first condition to a second condition in response to the predetermined annulus pressure.

It is a further object of the present invention to provide a locking apparatus adapted for locking a setting apparatus to a mandrel thereby preventing the mandrel from moving longitudinally relative to the setting apparatus and for unlocking the setting apparatus from the mandrel in response to a predetermined annulus pressure thereby allowing the mandrel to move longitudinally relative to the setting apparatus.

It is a further object of the present invention to provide a locking apparatus for unlocking a setting apparatus from a mandrel in response to a predetermined annulus pressure and setting a packer when the mandrel moves longitudinally relative to the setting apparatus.

It is a further object of the present invention to provide a locking apparatus for locking a drag block to a tubing string thereby preventing the drag block from moving longitudinally in a wellbore relative to the tubing string and to unlock the drag block from the tubing string in response to a predetermined annulus pressure thereby allowing the tubing to move longitudinally in the wellbore relative to the drag block, a packer being set when the tubing string is moved longitudinally in the wellbore relative to the drag block.

It is a further object of the present invention to provide a locking apparatus for locking a packer setting apparatus to a tubing thereby preventing normal operation of the packer setting apparatus in spite of manipulation of the tubing and for unlocking the packer setting apparatus from the tubing thereby allowing continued normal operation of the packer setting apparatus in response to manipulation of the tubing.

In accordance with these and other objects of the present invention, a tool string including a tubing, a packer, a packer setting apparatus, and a locking apparatus is adapted to be disposed in a wellbore. The locking apparatus locks the packer setting apparatus to the tubing and prevents any movement of the packer setting apparatus relative to the tubing. As a result, the packer setting apparatus is prevented from setting the packer in response to manipulative longitudinal movement of the tubing in the wellbore. However, when the locking apparatus unlocks the packer setting apparatus from the tubing, the packer setting apparatus may then move relative to the tubing. The packer setting apparatus may then set the packer in response to normal manipulative movement of the tubing in the wellbore. The locking apparatus includes a locking dog adapted to be disposed in a locking recess in a mandrel and a locking sleeve adapted for firmly holding the locking dog in the locking recess. The mandrel is connected to the tubing. Therefore, as long as the locking sleeve holds the locking dog in the locking recess of the mandrel, the locking apparatus locks the packer setting apparatus to the mandrel and to the tubing. As result, when the tubing moves longitudinally in the wellbore, the mandrel will also move, but the mandrel will not move relative to the tubing in response to any manipulative movement of the tubing in the wellbore. As a result, the packer cannot be set. However, when an annulus pressure in an annulus around the tool string exceeds a predetermined threshold pressure value, a rupture disc in the locking sleeve ruptures thereby allowing the annulus pressure to enter a chamber and move the locking sleeve away from the locking dog. When the locking sleeve moves away from the locking dog, any subsequent longitudinal movement of the mandrel moves the locking dog out of its locking recess. When the locking dog moves out of its locking recess, a sleevlet, connected to the locking dog, moves in the same direction as the locking dog thereby filling the locking recess originally occupied by the locking dog. When the sleevlet fills the locking recess, it is ratcheted in place thereby permanently filling the locking recess. When the locking recess is permanently filled, the lock is permanently removed. Therefore, the setting apparatus is free to move longitudinally, since it can no longer be prevented from moving downwardly in the wellbore. As a result, after the first hydraulic setting, the packer can be brought into a safety position by normal manipulation of the tubing.

Further scope of applicability of the present invention will become apparent from the detailed description presented hereinafter. It should be understood, however, that the detailed description and the specific examples, while representing a preferred embodiment of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become obvious to one skilled in the art from a reading of the following detailed description.

A full understanding of the present invention will be obtained from the detailed description of the preferred embodiment presented hereinbelow, and the accompanying drawings, which are given by way of illustration only and are not intended to be limitative of the present invention, and wherein:

FIG. 1 illustrates an overall construction of a packer apparatus having a plurality of packer elements, disposed above a locking apparatus in a wellbore, including a packer setting apparatus;

FIG. 2 illustrates one embodiment of the locking apparatus of FIG. 1 in accordance with the present invention.

FIGS. 3a-3b illlustrate the packer elements and another, preferred embodiment of the locking apparatus of FIG. 1 in accordance with the present invention, the locking apparatus being shown in the locked position;

FIGS. 4a-4c illustrate the packer elements and locking apparatus of FIGS. 3a-3b still in the locked position; however, the lock has been disabled thereby allowing the locking apparatus to be removed from the locked position and enabling the packer elements to be compressed;

FIG. 4a1 illustrates a slot in the mandrel wherein a jay-pin is disposed, the mandrel being connected to the tubing, the jay-pin moving within the slot between a safety position, a run-in position, and a set position in response to a manipulative longitudinal movement of the tubing and therefore the mandrel in the wellbore;

FIGS. 5a-5c illustrate the locking apparatus of FIGS. 4a-4c in the process of being removed from the locked position when a mandrel moves downwardly in the wellbore, the packer being in the process of being set;

FIGS. 6a-6c illustrate the locking apparatus of FIGS. 5a-5c removed from the locked position and the packer set in the wellbore; and

FIGS. 7a-7c illustrate the packer elements and locking apparatus of FIGS. 6a-6c still removed from the locked position but the packer is un-set in the wellbore.

Referring to FIG. 1, a conventional packer apparatus is illustrated. In FIG. 1, a mandrel 10 is connected to a tubing string 11 and is adapted to be moved upwardly and downwardly in a wellbore. A setting apparatus 20 is connected to the mandrel 10 and enables the setting of a packer 22 in response to a downward movement of the tubing 11 and mandrel 10 in the wellbore. The setting apparatus 20 includes a drag block 20a, the drag block 20a being slidingly connected to the mandrel 10 and being disposed in contact with the inner wall 16 of the wellbore. The drag block 20a of setting apparatus 20 functions to "drag" against the inner wall 16 of the wellbore in response to an upward and downward movement of the mandrel 10 produced by a manipulative, upward and downward longitudinal movement of the tubing string 11 in the wellbore. Although the drag block 20a will move relative to the inner wall 16 of the wellbore in response to a movement of the tubing 11, its contact with the inner wall 16 will cause the drag block 20a to "drag" against the inner wall 16 when the tubing 11 is moved downwardly in the wellbore. A slip bowl 12 moves into contact with packer slips 14 when the mandrel 10 moves downwardly in the wellbore and the drag block 20a drags against the inner wall 16 of the wellbore in response to a downward manipulative movement of the tubing at the wellbore surface. When the slip bowl 12 contacts slips 14, the slips 14 move radially outwardly until the slips 14 contact a wall 16 of the wellbore. When the slips 14 contact the wall 16 of the wellbore, further downward movement of the tubing 11 and mandrel 10 causes packer elements 18 to compress. As a result, the elements 18 of packer 22 contact the inner wall 16 of the wellbore. When the packer elements 18 contact and seal against inner wall 16 of the wellbore, the packer 22 is set in the wellbore thereby isolating a rathole annulus 24 below the set packer 22 from an annulus section 26 located above the set packer 22.

A locking apparatus 30, in accordance with the present invention, located below the setting apparatus 20, locks the mandrel 10 in its current position relative to the setting apparatus 20 thereby preventing any longitudinal movement of the mandrel 10 relative to the setting apparatus 20; in fact, the locking apparatus 30 prevents any longitudinal movement of the mandrel 10 relative to the drag block 20a and prevents any longitudinal movement of the slip bowl 12 relative to the slips 14. As long as the locking apparatus 30 maintains the lock on the mandrel 10 relative to the setting apparatus 20 and drag block 20a, when the tubing 11 is moved downwardly in the wellbore, the slip bowl 12 will not move relative to the slips 14 and therefore the elements 18 of packer 22 will not be set. The lock on the mandrel 10 relative to the setting apparatus 20 and drag block 20a is maintained until a predetermined threshold pressure is produced in the rathole annulus 24.

However, when a pressure in the rathole annulus 24 exceeds the predetermined threshold pressure, the lock of the mandrel 10 relative to the setting apparatus 20 and drag block 20a is removed. As a result, any further downward movement of mandrel 20 will cause the mandrel 10 to move relative to the drag block 20a and the slip bowl 12 to move relative to slips 14; therefore, slips 14 will contact wall 16 of the wellbore and the elements 18 of packer 22 will also contact wall 16 of the wellbore.

Referring to FIG. 2, a construction of a first embodiment of the locking apparatus 30 of FIG. 1, in accordance with the present invention, is illustrated. In FIG. 2, the slip bowl 12 is physically connected to the mandrel 10 and the slip 14 is connected to the locking apparatus 30. The mandrel 10 includes a locking recess 10a and a groove 10b in which a piece connected to the locking apparatus is disposed. The locking apparatus 30 comprises a locking dog 30a disposed in the locking recess 10a of the mandrel 10; a locking sleeve 30b includes a first end 30b1 which holds the locking dog 30a firmly into the locking recess 10a of mandrel 10, a second end 30b2, and an outwardly directed member 30b3 which includes a surface 30b3a; an outer housing 30c which includes a first end 30c1 which is disposed over the first end 30b1 of the locking sleeve 30b, a second end 30c2 which is disposed over and in contact with the second end 30b2 of the locking sleeve 30b and defines an atmospheric chamber 30c2a between the second end 30c2 of outer housing 30c and the outwardly directed member 30b3 of the locking sleeve 30b, and an inwardly directed member 30c3 which defines a space 30c3a between the inwardly directed member 30c3 and the outwardly directed member 30b3 of the locking sleeve 30b, the inwardly directed member 30c3 including a rupture disc 30c3b and a channel or port 30c3c which communicates an output channel of the rupture disc 30c3b to the space 30c3a and to the surface 30b3a of the outwardly directed member 30b3; a radially directable member or drag block 30d is connected to slip 14 and is always in frictional contact with wall 16 of the wellbore in response to the biasing force of a spring 30d1; and a piece known as a Jay pin 30e is disposed within the groove 10b and moves freely within groove 10b when the mandrel 10 moves longitudinally with respect to the locking apparatus 30.

A functional description of the operation of the locking apparatus 30 of FIG. 2 will be set forth in the following paragraph with reference to FIGS. 1 and 2.

Referring initially to FIG. 2 and subsequently to FIG. 1, as long as the locking dog 30a is disposed within the locking recess 10a, the mandrel 10 cannot move longitudinally relative to the outer housing 30c. Therefore, since the slip 14 is connected to the outer housing 30c, and the slip bowl 12 is connected to the mandrel 10, the slip bowl 12 cannot move into contact with the slip 14 as long as the locking dog 30a is disposed within the locking recess 10a. Since the slip bowl 12 cannot move into contact with the slip 14, the packer 22 of FIG. 1 cannot set. However, the rupture disc 30c3b is rated to rupture at a predetermined threshold pressure value. Therefore, when the pressure in the rathole annulus 24 exceeds the predetermined threshold pressure value, the rupture disc 30c3b will rupture. When the rupture disc ruptures, the pressure in the rathole annulus 24 will enter the rupture disc, enter the channel or port 30c3c, enter the space 30c3a, and exert its pressure on the surface 30b3a of the outwardly directed member 30b3 of the locking sleeve 30b. The pressure being exerted on surface 30b3a of outwardly directed member 30b3 will cause the locking sleeve 30b to move downwardly in FIG. 2. As a result, the first end 30b1 of the locking sleeve 30b will move away from and un-cover the locking dog 30a. Since the first end 30b1 has un-covered the locking dog 30a, the mandrel 10 can be moved downwardly relative to outer housing 30c in FIG. 2. When the mandrel 10 moves downwardly, the locking dog 30a moves out of its locking recess 10a. Jay pin 30e moves in the groove 10b. Since slip bowl 12 is connected to mandrel 10 and slip 14 is connected to the outer housing 30c, movement of mandrel 10 downwardly in FIG. 2 and movement of locking dog 30a out of locking recess 10a will enable the slip bowl 12 to contact slip 14 and will enable slip 14 to move radially outward and toward the wall 16 of the wellbore. When slip 14 contacts the wall 16 of the wellbore, further downward movement of mandrel 10 will compress the elements 18 of packer 22 of FIG. 1 and expand the elements 18 radially outwardly thereby setting the packer 22.

Referring to FIGS. 3a-3b, a detailed construction of a second, preferred embodiment of the locking apparatus 30 of FIG. 1 in accordance with the present invention is illustrated. FIGS. 3a-3b illustrate the second embodiment of the locking apparatus 30 in its initial run-in position, that is, the position of the locking apparatus when the tool of FIG. 1 is initially lowered into the wellbore and before the pressure in the rathole annulus 24 has been increased above a threshold pressure value.

In FIG. 3a, a packer 22 having elements 18 is concentrically installed on a mandrel 10. Slip bowl 12 is also concentrically installed on mandrel 10. The slip bowl 12 is adapted to move longitudinally with the mandrel 10. However, the slip bowl 12 will contact slips 14 when the mandrel 10 moves longitudinally in the downward direction in FIG. 3a relative to the slips 14. When the slip bowl 12 contacts slips 14, the slips 14 move radially into contact with the inner wall 16 of the wellbore. On the other hand, the slip bowl 12 cannot contact slips 14 as long as the locking apparatus 30 of FIG. 3b locks the slips 14 to the mandrel 10, which lock forces a drag block 14a to move with the mandrel 10 and prevents the slips 14 from contacting the slip bowl 12 as the mandrel 10 moves downwardly.

In FIG. 3b, a lower portion of a drag block 14a that includes slips 14 encloses the mandrel 10. The mandrel 10 includes a locking recess 10a. Locking dogs 30a are disposed in the locking recess 10a. A sleevlet 30f prevents the locking dogs 30a from moving downwards. A shoulder 10c prevents locking dogs 30a from moving upwardly. The sleevlet 30f includes teeth 30f1. Mandrel 10 also includes teeth 10b which are adapted to mate and ratchet with the teeth 30f1 of sleevlet 30f when the sleevlet 30f moves upwardly in FIG. 3b. A doglet 30g, attached to the drag block 14a, engages the sleevlet 30f and moves it against shoulder 10c as mandrel 10 moves downward. A springlet 30i resides in a recess disposed on the top of sleevlet 30f holding the sleevlet 30f firmly against a surface of mandrel 10. A locking sleeve 30b includes a first end 30 b1 adapted to hold the locking dogs 30a within its locking recess 10a when disposed in its position shown in FIG. 3b. The locking sleeve 30b also includes a second end 30b2, the second end 30b2 including a rupture disc 30b4 disposed therethrough. The rupture disc 30b4 communicates with a channel or port, this port further communicating with a surface 30h1 of a second sleeve 30h. The rupture disc 30b4 is rated at a predetermined threshold pressure value, the rupture disc rupturing when the pressure in annulus 26 of FIG. 1 exceeds the predetermined threshold pressure value.

Referring to FIGS. 4a and 4a1, a slot in the mandrel 10 is illustrated, and a jay-pin 30e rides within the slot. The jay-pin 30e moves within the slot between a safety position 30e3, a run-in (locked) position 30e2, and a set position 30e1 in response to a manipulative longitudinal movement of the tubing and therefore the mandrel 10 in the wellbore.

A functional description of the operation of the locking apparatus 30 of FIGS. 3a-3b will be set forth in the following paragraph with reference to FIGS. 3a-7c of the drawings. Element numerals used in FIGS. 3a-3b will also be used in FIGS. 4a-7c. FIGS. 4a-4c, 5a-5c, 6a-6c, and 7a-7c each illustrate the portion of the locking apparatus 30 shown in FIG. 3b of the drawings in various stages of functional operation.

Referring to FIGS. 3a-3b, although the tool string of FIG. 1 has been lowered into the wellbore, the packer 22 is un-set and no attempt has been made to set the packer 22. An operator at the well surface wants to set the packer 22.

In FIG. 3a, slips 14 have not been radially extended because slip bowl 12 still needs to be moved longitudinally in the downward direction to contact slips 14 and move the slips radially outwardly and into contact against the wall 16 of the wellbore.

In FIG. 3b, rupture disc 30b4 has not been disturbed. The one end 30b1 of the locking sleeve 30b holds the locking dog 30a firmly into its locking recess 10a. The locking sleeve 30b prevents the locking dog 30a from moving up and over the recess 10a when the mandrel 10 is moved downwardly in FIG. 3b, and the sleevlet 30f prevents the locking dogs 30a from moving downwardly relative to the mandrel 10 in FIG. 3b because the sleevlet 30f abuts against the locking dog 30a.

Referring to FIG. 4a-4c, the pressure in the rathole annulus 24 has been increased above the predetermined threshold pressure value, the rated pressure value of the rupture disc 30b4, and the locking sleeve 30b has been moved down and away from the locking dog 30a, un-covering the locking dog 30a.

In FIG. 4b, the pressure in the rathole annulus ruptures the rupture disc 30b4. The pressure enters the rupture disc and the pressure is exerted against the surface 30h1 of the second sleeve 30h. The resultant pressure build-up in the space below surface 30h1 moves the locking sleeve 30b downwardly in FIG. 4b. As a result, the one end 30b1 of locking sleeve 30b moves away from locking dog 30a, un-covering the locking dog 30a. However, in FIG. 4b, the locking dog 30a still remains in its locking recess 10a because the operator at the wellbore surface has not yet pushed downwardly on the mandrel 10. Therefore, the packer 22 remains in the un-set condition. The square shoulder on the sleevlet 30f prevents the dogs 30a from moving downwardly relative to the mandrel 10 and from accidentally jaying the packer 22 into a safety position that would require unwanted pipe manipulation to set the packer 22. Accidental jaying of the packer could be the result of pipe motion not generated by the operator at the surface, but by the pressure applied to the annulus that would tend to change the length of the tubing string.

Referring to FIGS. 3a, 5a-5c, the operator at the wellbore surface pushed downwardly on the mandrel 10; as a result, the locking dog 30a moved out of its locking recess 10a. Although the packer 22 is still un-set, it is now in the process of being set due to the downward movement of the mandrel 10.

In FIG. 3a, the slip bowl 12 contacts the slip 14; therefore, the slip 14 contacts the wall 16 of the wellbore. Due to the contact of slip 14 against the wall 16 of the wellbore, enough friction is built up to prevent the slip 14 from moving downwardly in response to a further downward push of the mandrel 10 by the operator at the wellbore surface.

In FIG. 5b, when the mandrel 10 moves further downwardly in response to the further downward push on the mandrel by the operator, since the one end 30b1 of the locking sleeve 30b has moved away and un-covered the locking dog 30a, the locking dog 30a is therefore free to move out of its locking recess 10a. In FIG. 5b, the locking dog 30a is no longer disposed in the locking recess 10a. As the mandrel 10 moves downwardly, the locking dog 30a slides along the surface of the mandrel 10. When the locking dog 30a begins to slide along the mandrel 10 surface, since the doglet 30g is connected to the locking dog 30a and is disposed in the recess of the sleevlet 30f (as seen in FIG. 4b), the doglet 30g pulls the sleevlet 30f upwardly; as a result, the teeth 30f1 on the sleevlet 30f mates or ratchets with the teeth 10b of the mandrel 10, the two sets of ratcheted teeth 10b/30f1 holding the sleevlet 30f firmly in place as shown in FIG. 5b. The sleevlet 30f now occupies the space originally occupied by the locking dog 30a. Therefore, the locking recess 10a, in which the locking dog 30a was originally disposed, has now disappeared and it no longer exists.

Referring to FIGS. 1, 3a, and 6a-6c, the operator at the wellbore surface continues to push downwardly on mandrel 10; as a result, the locking dog 30a continues to slide along mandrel 10.

In FIG. 1, the elements 18 of the packer 22 begin to engage and set against the wall 20 of the wellbore.

In FIG. 6b, due to continued downward movement of the mandrel 10, the locking dog 30a continues to slide along the surface of the mandrel 10 in what appears to be the upward direction. Sleevlet 30f is still held firmly in place by the ratcheted teeth 10b/30f1.

In FIG. 3a, since the slip 14 is still held firmly in place against wall 16 of the wellbore, any further downward movement of the mandrel 10 will compress and expand the elements 18 of packer 22; and, as the elements expand, the elements 18 eventually contact the inner wall 20 of the wellbore. The packer 22 is now set in the wellbore casing.

Referring to FIGS. 7a-7c, the packer 22 is set, but the operator at the wellbore surface now wishes to un-set the packer 22. The operator therefore pulls upwardly on the mandrel 10.

In FIGS. 7a-7b, since the operator has already pulled upwardly on the mandrel 10, the locking dog 30a slides along the surface of the mandrel 10. However, the sleevlet 30f is still held firmly in place by the ratcheted teeth 10b/30f1. Therefore, since the mandrel 10 is being pulled upwardly, and since the sleevlet 30f remains firmly in its position shown in FIG. 7b, the locking dog 30a must therefore slide over the top surface of the sleevlet 30f. Recall that the sleevlet 30f filled the locking recess 10a originally occupied by the locking dog 30a, and that the ratcheted teeth 10b/30f1 retain the sleevlet 30f in this position. As a result, when the mandrel 10 is pulled upwardly for the purpose of un-setting the packer 22, the upper shoulder of the sleevlet 30f does not prevent the locking dogs 30a from travelling further down; this allows the jay pin 30e to cycle to the safety position. From then on, the packer 22 can be set in a conventional manner, using rotation and upwards and downwards motion. See FIG. 4a1 for a view of the jay pin 30e in the set position 30e1, the run-in (locked) position 30e2, and the safety position 30e3.

In summary, the locking sleeve 30b originally holds the locking dog 30a in its locking recess 10a, prevents the slip bowl 12 from approaching the slip 14, and therefore engages a lock whereby the packer 22 is locked in the un-set condition. As long as the locking sleeve 30b holds the locking dog 30a in the locking recess 10a, the packer 22 cannot set. The packer 22 cannot set until the rupture disc 30b4 is ruptured. When the rathole annulus 24 pressure exceeds the predetermined threshold pressure value rating of the rupture disc 30b4, the rupture disc will rupture. Once the rupture disc 30b4 is ruptured, the locking sleeve 30b un-covers the locking dog 30a. Any subsequent downward push on mandrel 10 will set the packer 22, and sleevlet 30f will fill the locking recess 10a, the sleevlet 30f being ratcheted in place within the locking recess by ratcheted teeth 10b/30f1. Once the packer 22 is set, any subsequent upward pull on the mandrel 10 will un-set the packer 22. Since sleevlet 30f is held firmly in place within locking recess 10a by the ratcheted teeth 10b/30f1, the subsequent upward pull on the mandrel 10 will not re-engage the lock, and the packer 22 will be allowed to engage in the safety position of the J-slot for subsequent conventional operation.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.