US3096574A - Coil tie spacer cone and pulling device for the removal thereof from concrete installations - Google Patents

Description

July 9, 1963 B. HILLBERG 3,096,574

con, TIE SPACER CONE AND PULLING DEVICE FOR THE REMOVAL THEREOF FROM CONCRETE INSTALLATIONS Filed Aug. 50, 1957 INvENT E BROR HILLBERG ATTY United States Patent COIL TIE SPACER CONE AND PULLING DEVICE FOR THE REMOVAL THEREOF FROM CON- CRETE INSTALLATIONS Bror Hillberg, Franklin Park, 111., assignor, by mesne assignments, to Superior Concrete Accessories, Inc., a corporation of Delaware Filed Aug. 30, 1957, Ser. No. 681,359 7 Claims. (Cl. 29-263) The present invention relates to combined spreader and tie assemblies of the type which are designed to hold a pair of laterally spaced forms against inward collapsing or outward bulging during pouring of the concrete therebetween in connection with the formation of a wall or similar structure. More particularly the invention relates to a novel form of frusto-conical spacing member for such assemblies, as well as to a novel pulling device by means of which the frusto-conical spacing member may be dislodged from its embedded position within the concrete after the concrete has hardened and the forms have been removed.

The spreader and tie assemblies of the type with which the present cone-extracting pulling device is adapted to be employed involve in their general organization a strut which is adapted to be positioned between the two forms and which serves as a spreader means for the forms. This strut comprises a pair of parallel spaced apart rods, between which rods at the opposite ends thereof there is welded a pair of aligned helical thread-forming coils adapted to thneadedly receive therein respective lag bolts by means of which the forms are held against outward movement. When specifications require that the composite tie strut be completely embedded in the concrete structure within the confines of the wall faces, the spacer cones are in the form of frusto-conical spacing members which are partially threaded on the projecting ends of the helical thread-forming coils and fit between the ends of the struts and the inner faces of the forms so that when the lag bolts are tightened, these cones are firmly clamped between the inner faces of the forms and the ends of the struts. With the parts thus in position, the concrete is poured between the forms, and after hardening, when the forms are removed by withdrawal of the lag bolts, the cones remain at least partially embedded in the concrete with the large bases of the cone frusta exposed and lying flush with the outer faces of the concrete wall. Spreader and tie installations of the type briefly outlined above, and with which the present cone pulling device is associated, have been shown and described in my prior Patent No. 2,33 5,338, dated November 30, 1943 for Combined Spreader and Tie for Concrete Forms, and reference may be had to this patent for a full disclosure of the nature and operation of such assemblies.

In order to remove the frusto-conical spacer members, which will hereinafter be referred to simply as the spacer cones, it has been the practice to insert a wrench or similar tool having a square head designed to fit the square socket provided in the spacer cones for removal purposes and to unthread the cone from its threaded engagement with the end of its respective helical coil, thus breaking the bond between the outer frusto-conical face of the spacer cone and the surrounding concrete. Due to the fact that spacer cones of this sort are, for economy sake, invariably cast metal structures, they are frequently pos- 3,096,574 Patented July 9, 1963 ice sessed of surface irregularities. Furthermore, such cones are not always accurately round in transverse cross section. For these reasons it is often difficult to extract the cones by means of a conventional spacer cone wrench since the wrench affords no facility for pulling the cone longitudinally or axially from the conical socket in the concrete within which the cone is embedded. Where the cone is out-of-round, efforts to twist the cone within the socket merely effects a binding action wherein the cone becomes even more firmly lodged within the socket than it is when the same is in its free state. Surface irregularities, whether outwardly or inwardly extending similarly offer a high resistance to tortional stresses, as well as to outward movement of the cone from the socket despite the fact that the outward face of the cone is tapered. Another factor which contributes toward the dilficulty of removing the cone by conventional spacer cone wrenches resides in the bond which may be created between the internal threads provided in the cone and the threads afforded by the helical coil at the end of the spacer bars. Such a bond is often the result of rusting of the adjacent parts, i.e. the threads on the cone and the mating threads aiforded by the helical coil in the presence of the moisture present in the wet concrete when poured. Inasmuch as the convolutions of the helical coil are not welded together and are not individually welded to the longitudinal spacer bars or rods beyond the ends of the rods, these convolutions are tree and consequently resilient so that the entire projecting end of the coil is of a flexible resilient nature. The bond therefore is not easily broken by the application of torsional stresses to the cone by the application thereto of a spacer cone wrench, since the application of torque to the cone will simply have a tendency to twist the the helical coil and the latter does not offer sufiicient react-ion force to the twisting movement of the cone to cause the bond to become broken even though the bond between the cone and the surrounding concrete may be initially broken.

The present invention is designed to overcome the above-noted limitations that are attendant upon the use conventional spacer cones and spacer cone wrenches for removal of the cones from their positions of embedment in the surrounding concrete and, toward this end, the invention contemplates the provision of a novel tom of spacer cone, together with a novel form of cooperating cone puller assembly therefor, the latter, when applied to the cone according to the present invention being capable of exerting .a powerful direct axial pulling force on the cone to initially break the bond between the cone and the surrounding concrete and free the cone so that thereafter, with the pulling device still in position on the cone, torque may be applied to the cone so that the latter may be unthrca-ded from the helical coil with which it is associated in the tie rod assembly.

The provision of a cone pulling device of this general character and which will perform functions set forth by these convolutions will break away from their bonded union with the cone simultaneously thus freeing the cone in its entirety. Another object of the invention is to provide a spacer cone extracting device of this character have associated therewith one set of instrumentalities whereby a direct pulling force may be applied to the cone in an axial direction to initially break the bond between the cone and the surrounding concrete in which it is embedded, as well as a second set of instrumentalities designed for use, after the bond has been thus broken for applying torque to the cone to break any bond which may exist between the cone and the helical coil on which the cone is threaded.

In carrying out the above mentioned objects, briefly the invention contemplates the provision of a novel form of cone in which the central bore thereof is formed with a first threaded portion designed to receive therein the helical coil of the combined spreader and tie assembly in the usual manner of reception of such coils and also with a second threaded portion designed for threaded reception therein of a combined tension and torque ap plying member associated with the cone puller assembly. The two threaded portions of the bore are of opposite pitch so that when the tension and torque applying member is fully threadedly received within the second threaded portion of the bore and further turning movement is applied to the member torque will be applied to the cone in a direction tending to unthread the same from the helical coil. Means are provided whereby if, after such complete threaded engagement between the tension and torque applying member and cone is effected, the application of a reasonable amount of torque to the cone does not dislodge the same from its bond in the surrounding concrete, then a powerful axial pulling force may be applied to the tension and torque applying member, utilizing the outer surface of the concrete wall as a reaction member whereby such pulling force may be obtained. Accordingly, the tension and torque applying member is provided with a threaded portion over which there is received a tensioning nut. A thrust sleeve or collar is interposed between the tensioning nut and the outer face of the concrete wall when the pulling device is in operative position on the cone so that the nut may be tightened against the collar to force the latter against the outer face of the concrete wall and thus exert a direct pulling force on the tension and torque applying member so that the cone will be pulled axially outwardly from the surrounding concrete to thus initially break the bond between the cone and the concrete. With the bond between the cone and the concrete thus broken, the tension and torque applying member may be rotated about its longitudinal axis in a direction to cause the cone to become unthreaded from the helical coil associated with the spreader and tie assembly.

It is an additional object of the invention, in a spreader cone pulling device of the character briefly outlined above, to provide a piloting means whereby the combined tension and torque applying member of the cone puller assembly may be initially guided into and through the hollow spacer cone in such a manner that the threaded portion of the member will readily find threaded engagement with the central bore of the cone, and after such threaded engagement has been completely elfected, the piloting means will serve to maintain the pulling and torque applying member in axial alignment with the helical coil on which the cone is threaded so that upon the subsequent application of torque to the cone the convolutions of the coil will be maintained in axial alignment.

Yet another object of the invention is to provide a spacer cone pulling device having a combined pulling and torque applying member which makes threaded engagement with the cone undergoing pulling as mentioned above and which, furthermore, has associated therewith reaming means whereby any concrete adhering to the in- 4 ternally threaded portion of the cone after the lag bolt has been removed from the tie rod assembly will be effectively reamed from the cone so that the pulling and torque applying member may more readily find threaded engagement with the cone.

The provision of a cone pulling device which is extremely simple in its construction and which therefore may be manufactured at a relatively low cost; one which is comprised of a minimum number of parts, particularly relatively moving parts and which therefore is unlikely to get out of order; one which is rugged and durable and which is therefore possessed of a relatively long life, and one which otherwise is well adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

In the accompanying single sheet of drawings forming a part of this specification, one exemplary of the invention has been shown.

In these drawings:

FIG. 1 is a side view, partly in elevation and partly in section showing a spacer cone constructed in accordance with the principles of the present invention operatively installed in a combined tie and spreader assembly associated with a concrete wall construction, and showing the improved cone pulling device operatively applied to the cone for extraction purposes.

FIG. 2 is a sectional view taken substantially centrally and longitudinally through the spreader cone.

FIG. 3 is a bottom plan view of the cone shown in FIG. 2, and

FIG. 4 is an end view of the cone pulling device.

Referring now to the drawings in detail and in particular to FIG. 1,-a fragmentary portion of a partially knocked down concrete installation has been designated in its entirety at it]. The installation is in the form of a concrete wall 11 which is shown herein in horizontal section with the section being taken in the vicinity of one of a plurality of combined spreader tie assemblies 12 which serve as media for holding two for-ms against inward and outward movement :during pouring of the concrete therebetwcen in connection with the formation of the wall 11. For illustrative purposes herein only one form F is shown on one side of the wall 11, the opposing form being removed preparatory to removal of the various spreader cones from the outer face of the wall. The form F is of conventional design and includes the usual panels, one of which has been shown at 14, uprights 16 and waler pieces (not shown), through which waler pieces lag bolts 18 are adapted to extend for drawing the waler pieces against the uprights 16 to in turn maintain the panels 14 in their upright position against the tie and spreader assemblies 12. The details of the forms F have not been fully disclosed herein since they constitute no portion of the present invention. For a full disclosure of such a form reference may be had to my above mentioned patent which discloses the form and the manner in which the combined tie and spreader assemblies 12 are associated with the form.

The tie and spreader assembly 12 involves in its general organization a pair of parallel rods 20, a pair of closely wound helical coils 22, a pair of spacer cones 24, and a pair of the previously mentioned lag bolts 18. The helical coils 22 are arranged in axial alignment at the opposite ends of the rods 20 and are straddled by the adjacent ends of the pair of rods with the first several inner convolutions of each coil being welded in contiguity to the rods. The remaining or outer convolutions of each coil 22 project beyond the adjacent ends of the rods 20 and are normally free except insofar as the adjacent convolutions bear frictionally against each other. The two coils 22, in effect, constitute cylindrical members which are both internally and externally threaded to receive therein the threaded ends 29 of the lag bolts 18 as shown in the upper regions of FIG. 1, and to threadedly receive thereover the spacer this latter threaded section.

cones 24 as shown in both the upper and lower regions of FIG. 1.

The spacer cones 24 are in the form of tubular frustoconical members having central bores 28 therethrough and they are preferably formed of cast metal. To receive the convolutions at the outer end of the coil 22, the end of the bore 28 adjacent the small base of the cone frustum is threaded in one direction, for example, to present right hand threads 30. In order to -fit the outer surfaces of these convolutions and match the cylindrical cross-sectional configuration of the twisted rod stock of the coil, the threads have semi-cylindrical trough portions and sharp crest portions as clearly shown in FIG. 3. Threads of this nature are known in the art as contour threads and are commonly employed in connection with cast cone structures. The other end of the bore 28 is formed with a square socket-like recess 32 therein, and adjacent this recess a limited portion of the bore 28 is threaded so as to present internal reverse or left hand threads 34. The functions of the square recess 32 and of the reverse threads 34 will become clear as the following description ensues.

When the combined spreader and tie assembly is operatively disposed in an installation such as the installation disclosed in FIG. 1, the heads of the lag bolts 18 are disposed adjacent the outer faces of the horizontally extending waler s in the usual manner and the shanks of the bolts extend through holes 36 in the form panels 14 and project completely through the bores 28 in the spacer cones 24 and have their threaded ends 29 received in the helical coils 22. When the lag bolts are fully tightened they serve to clamp the spacing members and the forms against the ends of the rods 20 with the consequent result that the combined spreader and tie assembly 12 effectively holds the two forms against inward and outward displacement. After assembly of the various spreader and tie devices with the two forms, the concrete is poured into the space between the various panels 14 and allowed to become set, after which the lag bolts 18 are removed and the forms are dismantled or removed from the concrete structure. Thereafter, the frusto conical spacer members 24 are removed and the cavities left by such removal of these spacer members are filled with a mass of concrete so that the wall will present a smooth exterior surface.

Although the cones 24 may, under certain circumstances, conveniently be removed in a conventional manner by the application thereto of a suitable cone pulling wrench having a squared head designed for cooperation with the square socket-like recess 32 in the cone,

a more positive method of removing such cones is aflorded by the cone pulling device of the present invention. This cone pulling device has been designated in its entirety at 40 and it is comprised of four separate parts including a pull rod 42, a limit collar 44, a reaction sleeve 46 and a tensioning nut 48.

The pull rod 42 includes an elongated shank 50 having a torque-applying handle 52 suitably welded as at 54 to one end of the shank. The other end of the shank 50 is formed with a reduced pilot stem 56 adapted to be loosely received and piloted in the helical coil 22 associated with the particular spacer cone 24 undergoing extraction. inwardly of the pilot stem 56, the shank 44 is formed with a series of threads 58 designed for threaded reception in the threaded portion 34 of the spacer cone 24 when the pulling device is in its operative position as shown in FIG. 1. Adjacent the threads 58, the shank portion 50 is formed with a short cylindrical section 60 over which the limit collar 44 is received and on which it is secured for a purpose that will be made clear presently. A threaded section '62 of increased diameter extends between the handle 52 and cylindrical portion 60 and the reaction sleeve 46 is telescopically received over The tensioning nut 48 is threadedly received on the threaded portion 62 between the reaction collar 46 and handle 52 and is provided with a pair of oppositely disposed radially extending operating handles 64. The limit collar 44 is formed with a forward flat annular face 66 adapted to seat against the large base of the cone frustum afforded by the spacer cone 24 when the threaded portion 58 is fully received within the threaded portion 34 of the bore 28 in the spacer cone 24. To permit such seating of the limit collar 44 against the large base of the cone frustum, the collar 44 is loosely telescopically received over the cylindrical portion 60 of the shank 50 and is aflixed to this portion of the shank by means of a pin 68, the collar 44 being capable of limited rocking movement about the axis of the pin. The threaded portion 58 of the shank 50 is formed with a series of four circumferentially spaced longitudinally extending notches or grooves 70 (see also FIG. 2) the nature and function of which will be set forth presently.

In the use of the cone pulling device 40 for cone extracting purposes, the nut 48 is backed up on the shank 50 an appreciable distance and the shank 50 is inserted through the bore 28 in the cone 24 so that the pilot portion 56 thereof enters the helical coil 22, after which, by means of the handle 52, the shank 50 is turned to cause the threaded portion 58 of the shank to become threadedly received in the threaded portion 34 of the cone. Upon complete threaded engagement between these parts, the forward face 66 of the limit collar 44 will rest flush against the large base of the cone frustum with a limited amount of rocking movement of the collar being permitted to insure this flush engagement. Continued turning movement of the shank after such complete threaded engagement may, in certain instances, particularly where the cone is accurately circular in cross section and where there are no surface irregularities thereon so that the bond with the surrounding concrete is not tight, be sufficient to break the bond and permit extraction of the cone by outward pulling of the device 40 as a whole. In such an instance the function of the reaction sleeve 46 and tensioning nut 48 may be dispensed with. However, where the bond between the cone and the surrounding ooncrete is tight and where it resists such continued turning movement of the shank 50, the tensioning nut 48 will be drawn up tightly against the reaction sleeve 46 and the latter will obtain a reaction footing against the outer face of the concrete wall 11, after which continued turning movement of the nut 48 by means of the handle portion 64 will tightly wedge the reaction sleeve 46 between the nut and wall surface and exert a powerful pull on the cone 24 in a longitudinal direction tending to stretch the coil and break the bond between the cone and the concrete and allow its extraction. Because of the fact that the threaded portions 58 and 62 of the shank 50 are opposite in direction, there will be no tendency upon tightening of the nut 48 for the shank to become unthreaded from the cone 24.

It is to be observed that initial threaded engagement between the threaded portion 58 of the shank 50 and the threaded portion 34 of the cone bore 28 is facilitated by the provision of the reaming grooves or notches 70. As shown at the right hand side of FIG. 1, since the diameter of the lag screw 18 is somewhat less than the internal diameter of the helical coil 22, the annular space existing between the lag screw and coil will become filled with concrete during the pouring operations. This annular mass of concrete becomes hardened and remains as an inner lining or crust within the coil 22 when the lag screw 18 is initially removed. The reaming grooves or notches 70 create sharp edges on the screw threads 58 which have a reaming eifect on this inner crust or shell of concrete and dislodge the concrete so that threaded engagement between the threaded parts 34 and 58 may readily be effected when the shank is initially introduced into the bore 28 of the cone 24. The pilot stem portion 56 of the shank 50 maintains the various parts in axial alignment and thus further facilitates initial entry or the threaded portion 58 into the threaded portion 34. After the bond between the cone 24 and surrounding concrete has been initially broken the cone 24 will become completely separated from the surrounding concrete so that further turning movement thereof will be resisted only by the bond which may exist between the threaded portion 39 of the come 24 and the outer threaded surface of the helical coil 22. This bond may be the result :of rusting between the parts during setting of the moist concrete. As soon as the bond is initially broken between the outer surface of the cone 24 and the surrounding concrete, the reaction sleeve 46 and tensioning nut 48 will be relieved of tension so that further turning movement of the shank may be effected utilizing the handle 52 to thus unscrew the cone 24 from the helical coil 22. The pilot portion 56 of the shank 50 will maintain the shank in accurate axial alignment with the coil 22 so that there will be no tendency for the coil to become distorted at any point of weakness which may exist along its extent. The direction of turning movement of the shank 5% during such unthreading operation is such that the limit collar 44 will remain in engagement with the large base of the cone frustum so that the necessary degree of torque may be applied to the shank 50 to effect breaking of the bond between the cone 24 and coil 22. After such bond has been broken and the cone turned out of threaded engagement with the coil 22, the entire device 40 may be pulled bodily outwardly away from the wall 11 thus drawing with it the cone 24. The cone may thereafter be unthreaded from the threaded portion 58 of the shank 50 and thus salvaged while at the same time the pulling device 40 will be ready for use in the eX- traction of a succeeding cone 4.

A preferred form of the improved spacer cone extracting device and spacer cone construction has been shown in the drawings and described herein. The specific disclosure however is purely exemplary and it should be understood that the invention is not to be limited to this disclosure since various changes in the details of construction may be resorted to without departing from the spirit of the invention. The appended claims should therefore be construed as broadly as the prior art will permit.

Having thus described the invention what I claim and desire to secure by Letters Patent is:

l. The combination with a frusto-conical spacer member having a central bore extending axially therethrough, the end of the bore adjacent the small base of the cone trustum being provided with a first series of internal right hand threads, another portion of the bore adjacent the large base of the cone frustum being formed with a series of left hand threads, of a cone puller device for extracting said spacer member from a position of embedment in a mass of hardened concrete wherein said series of right hand threads are threadedly received on the free closely wound convolutions of a hollow coil tie embedded in said mass, said cone puller device comprising an elongated pull rod having a torque applying handle at one end thereof, the other end of said pull rod being formed with a serie of threads for mating engagement with said series of left hand threads, and means on said pull rod providing a shoulder to limit the extent of threaded reception of the pull rod by said series of left hand threads, whereby upon continued turning movement of the pull rod after complete mating engagement with said series of left hand threads, the spacer member will be turned bodily with the pull rod to initially loosen the same from the surrounding concrete and to thereafter cause the same to become unthreaded from said coil tie.

2. The combination set forth in claim 1 wherein the series of threads on said pull rod are interrupted by a series of longitudinally extending circumierentially spaced notches formed in the pull rod and intersecting the series of threads on the pull rod whereby the tooth fragments between adjacent notches constitute reaming means for dislodging any concrete which may have adhered to said left hand threads from a previous concrete installation.

3. The combination set forth in claim 2, including, additionally, a pilot extension formed on and extending axially from the threaded end of said pull rod and designed for reception in the coil tie to maintain the pull rod and coil tie in axial alignment during unthreading operations.

4. The combination with a trusto-conical spacer member having a central bore extending axially therethrough, the end of the bore adjacent the small base of the cone irustum being provided with a first series of internal threads, another portion of the :bore adjacent the large base of the cone frustum being formed with a second series of internal reverse threads, of a cone puller device for extracting said spacer member from a position of embedment in a mass of hardened concrete wherein said first threads are threadedly received on an externally threaded portion of a hollow coil tie embedded in said mass, said cone puller device comprising an elongated pull rod having a torque applying handle at one end thereof, the other end of said pull rod being formed with a series of threads for mating engagement with said reverse threads, means on said pull rod providing a shoulder to limit the extent of threaded reception of the pull rod by said reverse threads, whereby upon continued turning movement of the pull rod after complete mating engagement with said threads of reverse pitch, the spacer member will be turned bodily with the pull rod to initially loosen the same from the surrounding concrete and to thereafter cause the same to become unthreaded from said coil tie, and tensioning means for applying a longitudinal pulling force on said pull rod after the same has become threaded into said reverse threads, said tensioning means comprising an additional series of thread on said pull rod between said torque applying handle and shoulder-providing means, and a tensioning nut threadedly received on said latter series of threads and designed to be effectively tightened against said mass of concrete for reaction purposes.

5. The combination set forth in claim 4 wherein said tensioning means comprises, additionally, a reaction collar loosely received on said pull rod and slidable therealong, said reaction collar being disposed between the tensioning nut and concrete mass.

6. The combination set forth in claim 4 including, additionally, a pair of operating handles secured to and extending radially outwardly in opposite directions from the opposite sides of said tensioning nut.

7. The combination with a frusto-conical spacer memher having a central bore extending axially therethrough, the end of the bore adjacent the small base of the cone frustum being provided with a first series of internal threads, another portion of the bore adjacent the large base of the cone frustum being formed with a series of internal reverse threads, of a cone puller device for extracting said spacer member from a position of embedment in a mass of hardened concrete wherein said first threads are threadedly received on an externally threaded portion of a hollow coil tie embedded in said mass, said cone puller device comprising an elongated pull rod having a torque applying handle at one end thereof, the other end of said pull rod being formed with a series of threads for mating engagement with said reverse threads, means on said pull rod providing a shoulder to limit the extent of threaded reception of the pull rod by said reverse threads, whereby upon continued turning movement of the pull rod after complete mating engagement with said reverse threads, the spacer member will be turned bodily with the pull rod to initially loosen the same from the surrounding concrete and to thereafter cause the same to become unthreaded from said coil tie, and tensioning means for applying a longitudinal pulling 9 force on said pull nod after the same has become threaded into said reverse threads, said tensioning means comprising an additional series of threads on said pull rod between said torque applying handle and shonldenproviding means, a tensioning nut threadedly received on said latter series of threads, a reaction cup slidable on said pull rod between said tensioning nut and mass of concrete and designed for engagement with the latter when the tensioning nut is tightened against the cup, said reaction cup encompassing said shoulder-providing means when the cup is in position against said mass of concrete, and an operating handle on said tensioning nut.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. THE COMBINATION WITH A FRUSTO-CONICAL SPACER MEMBER HAVING A CENTRAL BORE EXTENDING AXIALLY THERETHROUGH, THE END OF THE BORE ADJACENT THE SMALL BASE OF THE COME FRUSTUM BEING PROVIDED WITH A FIRST SERIES OF INTERNAL RIGHT HAND THREADS, ANOTHER PORTION OF THE BORE ADJACENT THE LARGE BASE OF THE CONE FRUSTUM BEING FORMED WITH A SERIES OF LEFT HAND THREADS, OF A CONE PULLER DEVICE FOR EXTRACTING SAID SPACER MEMBER FROM A POSITION OF EMBEDMENT IN A MASS A HARDENED CONCRETE WHEREIN SAID SERIES OF RIGHT HAND THREADS ARE THREADEDLY RECEIVED ON THE FREE CLOSELY WOUND CONVOLUTIONS OF A HOLLOW COIL TIE EMBEDDED IN SAID MASS, SAID CONE PULLER DEVICE COMPRISING AN ELONGATED PULL ROD HAVING A TORQUE APPLYING HANDLE AT ONE END THEREOF, THE OTHER END OF SAID PULL ROD BEING FORMED WITH A SERIES OF THREADS FOR MATING ENGAGEMENT WITH SAID SERIES OF LEFT HAND THREADS, AND MEANS ON SAID PULL ROD PROVIDING A SHOULDER TO LIMIT THE EXTENT OF THREADED RECEPTION OF THE PULL ROD BY SAID SERIES OF LEFT HAND THREADS, WHEREBY UPON CONTINUED TURNING MOVEMENT OF THE PULL ROD AFTER COMPLETE MATING ENGAGEMENT WITH SAID SERIES OF LEFT HAND THREADS, THE SPACER MEMBER WILL BE TURNED BODILY WITH THE PULL ROD TO INITIALLY LOOSEN THE SAME FROM THE SURROUNDING CONCRETE AND TO THEREAFTER CAUSE THE SAME TO BECOME UNTHREADED FROM SAID COIL TIE.

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