Snap Lock, Anti-Reverse Rotation Coupler Assembly for Foundation Support System

This application is a continuation application of U.S. application Ser. No. 18/351,613 filed Jul. 13, 2023, which claims the benefit of U.S. Provisional Application Ser. No. 63/394,073 filed Aug. 1, 2022, the complete disclosure of which is hereby incorporated by reference in its entirety.

This application further relates in part to subject matter disclosed in U.S. application Ser. No. 17/174,805 filed Feb. 12, 2021 and now issued U.S. Pat. No. 12,338,598, which claims the benefit of U.S. Provisional Application Ser. No. 62/976,442 filed Feb. 14, 2020, the entire disclosures of which are hereby incorporated by reference in their entirety.

The field of the invention relates generally to building foundation support systems including assemblies of coupled structural support shaft components, and more specifically to improved torque transmitting couplings for foundation support shaft components such as helical piers.

If a building foundation moves or settles in the course of construction, or at any time after construction is completed, such movement or settlement may affect the integrity of the building structure and lead to costly repairs. While much care is taken to construct stable foundations in new building projects, certain soil types or other building site conditions, or certain types of buildings or structures, may present particular concerns that call for additional measures to ensure the stability of building foundations.

Helical piers, also known as anchors, piles or screw piles, are deep foundation solutions commonly used when standard foundation solutions are problematic. Helical piers are driven into the ground with reduced installation time and little soil disturbance compared to large excavation work that may otherwise be required by standard foundation techniques, and a number of helical piers may be installed at designated locations to transfer and distribute the weight of the building structure to load bearing soil to prevent the foundation from moving or shifting. Lifting elements, support brackets or load-bearing caps may be used in combination with the helical piers to construct various types of foundation support systems meeting different needs for both foundation repair and new construction applications.

While known foundation support systems are satisfactory in many aspects, improvements are nonetheless desired.

In order to understand the inventive concepts described herein to their fullest extent, some discussion of the state of the art and certain problems and disadvantages that exist in the art is set forth below, followed by exemplary embodiments of improved foundation support systems and components therefore which overcome such problems and disadvantages in the art.

illustrates a perspective view of a conventional foundation support systemin combination with a building foundationwhich in turn supports a structure in residential, commercial or industrial construction site. The structure being supported by the building foundationmay include various types of buildings, homes, edifices, etc. in real estate developments and improvements. The foundation support systemmay be applied in the new construction of the building foundationprior to the structure being completed, or may alternatively be applied for maintenance and repair purposes in a retrofit manner to a pre-existing building foundation at any desired time after the foundationand building structure are initially constructed. While exemplary structures are mentioned above, the foundation support systemmay be used in a similar manner to provide foundation support for various different types of structures and to securely support anticipated structural loads without more extensive excavation that standard building foundations otherwise require to provide a similar degree of support. The foundation support system described and illustrated herein is therefore a non-limiting example of the type of system that may be benefit from the inventive concepts described further below.

Primary piles or pipe shafts (hereinafter collectively referred to as a “pile” or “piles”)of appropriate size and dimension may be selected and may be driven into the ground or earth at a location proximate or near the foundationusing known methods and techniques. The size of the primary pileand the insertion depth needed to provide the desired support may be determined according to known engineering methodology and analysis of the construction site and the particular structure that is to be supported. The primary pilestypically consist of a long shaftthat is driven into the ground to the desired depth, and a support element such as a plate or bracket (not shown) or a lifting element such as a lifting assemblymay be assembled to the shaftproximate the foundation. The shaftof the primary pilemay also include one or more lateral projections such as a helical auger. Such helical steel pilesare available from, for example, Pier Tech Systems (www.piertech.com) of Chesterfield, Missouri.

The helical augermay in some embodiments be separately provided from the pilingand attached to the pilingby welding to a sleeveincluding the augerprovided as a modular element fitting. As such, the sleeveof the modular fitting may be slidably inserted over an end of the shaftof the piling shaftand secured into place with fasteners such as bolts as shown in. In such an embodiment, the sleeveincludes one or more pairs of fastener holes or openings for attachment to the piling shaftwith the fasteners shown. In the embodiment illustrated there are two pairs of fastener holes formed in the sleeve, which are aligned with corresponding fastener holes in the shaftto accept orthogonally-oriented fasteners and establish a cross-bolt connection between the shaftand the sleeve. To make a primary pilewith a particular length one merely slides the sleeveonto a piling shaftof the desired length and affixes the sleevein place. In the illustrated embodiment, the end of the piling shaftis provided with a beveled tipto better penetrate the ground during installation of the pile. In different embodiments, the tapered tipmay be provided on the shaftof the piling, or alternatively, the tipmay be a feature of the modular fitting including the sleeveand the auger.

The lifting assemblymay be attached to an upper end of the primary pileafter being driven into the ground. If the primary pileis not sufficiently long enough to be driven far enough into the ground to provide the necessary support to the foundation, one or more extension pilescan be added to the primary pileto extend its length in the assembly. The lifting assemblymay then be attached to one of the extension piles.

As shown in, the lifting assemblyinteracts with the foundationto support and lift the building foundation. In a contemplated embodiment, the lifting assemblymay include a bracket body, one or more bracket clampsand accompanying fasteners, a slider block, and one or more supporting boltswhich may be allthread rods, for example, and accompanying hardware. In another suitable embodiment the lifting assemblymay also include a jackand a jacking block. Suitable lifting assemblies may correspond to those available from Pier Tech Systems (www.piertech.com) of Chesterfield, Missouri, including for example only the TRU-LIFT® bracket of Pier Tech Systems, although other lifting assemblies, lift brackets, and lift components from other providers may likewise be utilized in other embodiments.

The bracket bodyin the example shown includes a generally flat lift plate, one or more optional gussets, and a generally cylindrical housing. The lift plateis inserted under and interacts with the foundation or other structurethat is to be lifted or supported. The lift plateincludes an opening, with which the cylindrical housingis aligned to accommodate one of the primary pileor an extension pile. The housingis generally perpendicular to the surface of lift plateand extends above and below the plane of lift plate.

In the example shown, one or more gussetsare attached to the bottom surface of the lift plateas well as to the lower portion of the housingto increase the holding strength of the lift plate. In one embodiment, the gussetsare attached to the housingby welding, although other secure means of attachment are encompassed within this invention.

In the example shown, the bracket clampsinclude a generally Ω-shaped piece having a center hole at the apex of the “Ω” to accommodate a fastener. The Ω-shaped bracket clampincludes ends, extending laterally, that include openings to accommodate fasteners. The fasteners extending through the openings in the endsare attached to the foundation, while the fastener extending through the center opening at the apex of the “Ω” extends into an opening in the housing. In one embodiment the fastener extending through the center opening in the bracket clampand into the housingfurther extends through one of the primary pileor the extension pileand into an opening on the opposite side of the housing, and then anchors into the foundation. In such cases, however, the fastener is not inserted through one of the primary pileor the extension pileuntil jacking or lifting has been completed, since bracket bodymust be able to move relative to pileorin order to effect lifting of the foundation.

In one embodiment, the bracket bodyis raised by tightening a pair of nutsattached to the top ends of the supporting bolts. The nutsmay be tightened simultaneously, or alternatively, in succession in small increments with each step, so that the tension on the boltsis kept roughly equal throughout the lifting process. In another suitable embodiment, the jackis used to lift the bracket body. In this embodiment, longer support boltsare provided and are configured to extend high enough above the slider blockto accommodate the jackresting on the slider block, the jacking block, and the nuts.

When all of the components are in place as shown and sufficiently tightened, the jack(of any type, although a hydraulic jack is preferred) is activated so as to lift the jacking plate. As the jacking plateis lifted, force is transferred from the jacking plateto the support boltsand in turn to the lift plateof the bracket body. When the foundationhas been lifted to the desired elevation, the nuts immediately above the slider block(which are raised along with support boltsduring jacking) are tightened down, with approximately equal tension placed on each nut. At this point, the jackcan then be lowered while the bracket bodywill be held at the correct elevation by the tightened nuts on the slider block. The jacking blockcan then be removed and reused. The extra support bolt material above the nuts at the slider blockcan be removed as well, using conventional cutting techniques.

The lifting assemblyand related methodology is not required in all implementations of the foundation support system. In certain installations, the foundationis desirably supported and held in place but not moved or lifted, and in such installations the lifting assembly shown and described may be replaced by a support plate, support bracket or other element known in the art to hold the foundationin place without lifting it first. Support plates, support brackets, support caps, and or other support components to hold a foundation in place are available from Pier Tech Systems (www.piertech.com) of Chesterfield, Missouri and other providers, any of which may be utilized in other embodiments of the foundation support system.

As mentioned, it is sometimes necessary to extend the length of a piling by connecting one or more shafts which in combination may provide support that extends deeper into the ground than the shafts individually can otherwise reach. For example, a first helical pier component, referred to as a primary pile, may be driven nearly fully into the ground at the desired location, and a connection component such as an extension pile may then be attached to the end of the primary pile in order to drive the primary pile deeper into the ground while supporting the building foundation at an end of the extension pile. More than one extension pile may be required depending on the lengths of the piles available and/or particular soil conditions.

are a side view and sectional view, respectively, of a coupler assembly that overcomes some of the drawbacks of prior couplers for foundation support systems such as that shown in. Specifically,illustrate a snap-lock coupler system in the form of couplers,that advantageously avoid any need for separately provided fasteners such as bolts to interconnect shafts associated with each respective coupler,. The couplerincludes a shaft receiving endfor a first shaft, and the couplerincludes a shaft receiving endfor a second shaft. The shafts associated with each coupler,may be, for example, primary piles and/or extension piles in the foundation support system. In lieu of bolts to maintain an engagement of the couplers,an annular spring elementis provided on the couplerthat automatically operates with snap-action engagement to axially interlock the couplers,to one another.

The coupleris formed with a main bodydefining a central passageway or bore having an inner surface with an inner diameter about equal to, but slightly larger than the outer diameter of a main bodyof the coupler. The couplerincludes a circumferential retaining grooveformed in its outer surface adjacent a distal end of the coupler, and the annular spring retainer elementextends in the retaining groove.

The main bodyof the coupleris formed with a number of outwardly projecting spaced apart and helically extending ribsthat are mated with complementary helical groovesformed on an inner surface of the main bodyof the coupler. As the couplers,are mated, the ribsdeflect the annular spring retainer elementto enlarge its diameter until the spring retainer elementresiliently snaps back to its original diameter. After snapping back to the original diameter, the spring retainer elementextends in a combination of the retaining grooveof the couplerand an aligned retaining groove formed in the coupler.

By virtue of the snap-action engagement of the couplers,the assembly of the couplers to make the desired interconnections of shafts is simplified, and issues associated with conventional separately provided fasteners such as bolts to make the desired interconnections of the shafts through the couplers is avoided. The spring retainer elementprovides an axial interlock of the engaged couplers,while the ribsand grooves+simultaneously provide both axial and rotational interlock of the couplers,. Because the helical ribsand groovesdistribute any uplift forces in the mated outer and inner surfaces of the couplers,, the spring retainer elementmay be smaller and lighter than it otherwise may need to be if it exclusively bore all of the uplift forces that may be presented.

The snap-lock coupler system shown inis more completely described in U.S. Patent Application Publication No. 2021/0254298 of Pier Tech Systems. The reader is therefore referred to the same for further details.

While the snap-lock couplers,solve significant problems presented in conventional foundation support systems and work well in certain installations, the present inventors have realized certain limitations presented in the snap-lock couplers,for certain end-use installations and installation methods. Specifically, the mated helical ribsand helical groovesin the couplers,were designed and intended to provide secure rotational interlock to transmit torque in either direction (forward or reverse) to drive a piling deeper into the ground or to partially or completely withdraw it from the ground, without requiring a separately fastener such as a bolt to complete the torque transmitting connection. While the inventors confirm that the mated helical ribsand helical groovesin the couplers,do provide secure rotational interlock to transmit torque in a forward direction as a helical pile is being driven into the ground, when the coupler assembly is subjected to reverse rotation a relative rotation of the couplers,is possible. That is, the expected rotational interlock of the couplers,in reverse rotation is not necessarily present, and relative reverse rotation of the couplers,with respect to one another may be problematic in some installations.

The inventors have observed an unexpected result in that the helical ribsexhibit a tendency to back out of the helical grooveswhen rotated in reverse. In other words, the helical ribsare prone to moving longitudinally in the helical groovesin a manner that the helical ribs, if not impeded, would axially withdrawal from the helical groovesand realize separation of the couplers,when the coupler assembly is subject to reverse rotation. The spring retainer elementoperates to inhibit such withdrawal and associated separation of the couplers,and instead maintain the ribsfully engaged in the grooves. But this imposes an undesirable stress on the spring retainer elementthat can compromise the connection between the couplers,as reverse rotational force (i.e., torque) increases. In certain cases, torsional forces can rise to levels wherein the spring elementexperiences shear stress to the point of failure, leaving the couplers,effectively uncoupled in the axial direction. If uplift forces are also present in this state, the couplers,can undesirably separate from one another in a manner that would defeat the integrity of the foundation support system. Considering that this may happen at a below ground location that may be difficult to detect, the building foundation may not be adequately supported despite the presence of the foundation support system.

Additionally, and apart from any reverse rotation that tends to withdraw the helical ribsfrom the helical groovesand separate the couplers,, similar dynamics can result when the coupler assembly is subjected to uplift forces that tend to pull the couplers,apart. Initially the spring elementwill operate to oppose the uplift forces and maintain engagement of the ribsand grooves, but if uplift forces are sufficiently high, stress imposed on the spring elementmay cause it to shear and effectively uncouple the couplers with potential to defeat the integrity of the foundation support system.

are various views of a coupled shaft assemblyfor the foundation support systemshown inin accordance with an exemplary embodiment of the present invention that beneficially overcomes the limitations of the snap-lock coupler system shown in. Method aspects of the inventive couplers will be in part apparent and in part explicitly discussed in the following description.

The coupler assemblyin the example shown includes a first or outer couplerprovided on a first shaftwhich may be an extension pile in a foundation support system such as that shown in. The coupler assemblyalso includes a second or inner couplerprovided on a second shaftwhich may be a primary pile in a foundation support system such as that shown in. Alternatively the shafts,may each be extension piles in a foundation support system. It is recognized, however, the that shafts,need not be primary or extension foundation support pile elements at all, and instead the couplers,may be used in a wide variety of pipe or shaft systems that present similar problems and concerns to those discussed above or that may benefit from the coupling features described herein in another end use or application besides a foundation support system.

The couplers,including the features illustrated and described further below may be separately manufactured from the shafts,in certain embodiments, and thereafter attached to each shaft,in a known manner, including but not necessarily limited to welding. Alternatively, the couplers,may be integrally formed on respective ends of the shafts,via casting, forging and swaging processes instead of separately provided and attached elements. The couplers,and the shafts,may each be fabricated from high strength steel or another suitable material according to known techniques.

The shafts,connected through the couplers,can be hollow or filled with a substance such as concrete, chemical grout, or another known suitable cementitious material or substance familiar to those in the art to enhance the structural strength and capacity of the shafts when used as foundation support pilings or in other end use applications. The pilings defined by the connected shafts,may be prefilled with cementitious material in certain contemplated embodiments.

Likewise, in other contemplated embodiments, cementitious material, including but not necessarily limited to grout material familiar to those in the art, may be mixed into the soil around the piles as they are being driven into the ground, creating a column of cementitious material around the pilings for further structural strength and capacity to support a building foundation. Grout and cementitious material may be pumped through the hollow pilings under pressure as the pilings are advanced into the ground, causing the hollow pilings to fill with grout, some of which is released exterior to the pilings to mix with the soil at the installation site. Openings and the like can be formed in the piles to direct a flow of cementitious material through the piles and at selected locations into the surrounding soil.

Like the couplers,shown in, a spring retainer elementis provided to automatically interlock the couplers,with a desired snap-action. Also like the couplers,shown in, the spring elementis enlarged in diameter as the couplers,are engaged, and resiliently snaps back to its original diameter in a state occupying circumferential retaining grooves in each of the couplers,as shown in.

As shown in, and unlike the annular springof the couplers,that is generally planar and shaped to extend around the circumference of the coupler ends for less than 360° as described in U.S. Patent Application Publication No. 2021/0254298, the spring elementextends in the circumferential grooves of the couplers,well beyond 360° around the circumference of the couplers. In the illustrated example, the spring elementextends in a spiral arrangement that from end-to-end completes a bit less than three full 360° turns around the circumference of the couplers,. Of course, a multi-turn spring elementhaving greater or fewer than about three full 360° turns may be utilized in alternative embodiments with similar effect. The spring elementhas a rectangular cross section and a low profile in the height dimension to fit within the associated grooves in the couplers,in a compact arrangement as shown in.

In contemplated embodiments, the spring elementis fabricated from a resiliently deflectable metal material, metal alloy or another suitable material allowing the spring retainer elementto elastically expand in the radial dimension from an initial diameter to a larger diameter when subjected to an outwardly directed force, and return to its initial diameter when the outwardly directed radial force is removed.

Relative to a fractional turn spring element like the annular spring element(i.e., a spring element that completes less than one full 360° turn in the circumferential grooves of the couplers,), such a multi-turn spring elementprovides additional structural strength and spring force for the desired snap-action engagement in the foundation support application whiles still beneficially avoiding any use of separately provided fasteners such as bolts to complete the desired interconnections of shafts,. In the context of the present description, the increased structural strength of the multi-turn spring elementmakes it accordingly less prone to problematic shearing than the annular, planar elementof the couplers,when the couplers,are subjected to reverse rotation and/or uplift forces in use. Additional structure, however, is beneficially provided in the couplers,providing only a predetermined degree of relative reverse rotation of the couplers,and an independent axial interlock coupling apart from the spring elementwhen needed. By virtue of such additional structure, the couplers,therefore reduce, if not eliminate, any chance that the spring elementcould mechanically fail at an underground location to due to mechanical shear stress or overload associated with reverse rotation and/or uplift forces.

Specifically, and as further described below, anti-reverse rotation features are built-in to the rib and groove design of the couplers,that ensure that a problematic relative rotation and separation of the couplers,will not occur if the shaft, for example, is subjected to reverse rotation in the installation of a foundation support system and/or is subjected to uplift forces in use. In the coupler assembly, and by virtue of the built-in anti-reverse rotation features in the ribs and grooves, rotational and uplift forces are borne between mating ribs and grooves formed in the couplers,as further described below. Separately provided anti-reverse rotation elements, including but not limited to fasteners such as bolts, are therefore desirably avoided by the built-in anti-reverse rotation features of the couplers,, and no action is needed by an installer to address reverse rotation issues with separately provided elements in the installation of a foundation support system.

As seen in, the outer couplerincludes a hollow main bodyand a shaft receiving end. The main bodyincludes an inner surfacehaving a first set or first series of spaced apart groovesdepending inwardly therefrom. The main bodyfurther includes an outer surfacedefining a second set or series of retaining groovesfor the spring element. In the illustrated example, the main bodyis cylindrically shaped with a round, circular cross section having a uniform or constant inner and outer diameter along an axial centerline of the main body in the coupler. In an alternative embodiment, however, the main bodymay have a tapered inner and outer diameter such that the inner and outer diameter may change (e.g., may increase) along an axial centerline of the main body.

The spring elementis pre-installed and permanently attached to the coupler(i.e., the spring retainer elementis not intended to be removed) via the groovesand is therefore integrated into the coupler design in contemplated embodiments as shown in. This allows the couplerto be provided to the installer with the spring retainer elementalready in place, eliminating any need for an installer to locate a spring element. By virtue of the spring element, a separately provided fastener (or fasteners) including but not necessarily limited to conventional bolts to attach piles to one another in conventional foundation support systems is not required. Associated installation steps of installing separately provided fasteners (e.g., bolts) are eliminated and installation time and labor costs associated with such installation steps are desirably eliminated.

As seenand also the views of, the inner couplerincludes a hollow main bodyand a shaft receiving endin the illustrated example. The main bodyalso includes an outer surfacehaving a series of spaced apart ribsprojecting outwardly therefrom. Each ribalso includes an outer surface defining a retaining groovefor the spring elementas shown in. Once the couplers,are engaged, the spring elementresides in part in the retaining groovesof the couplerand in part in the aligned retaining groovesof the coupleras shown in.

In the illustrated example, the main bodyis cylindrically shaped with a round, circular cross section having a uniform or constant inner and outer diameter along an axial centerline of the main body in the coupler. In an alternative embodiment, however, the main bodymay have a tapered inner and outer diameter such that the inner and outer diameter may change (e.g., may decrease) along an axial centerline of the main body.

Referring to, the main bodyof the inner coupleris formed with a number of distinct, outwardly projecting spaced apart and helically extending ribsprojecting from outer surface. In the example shown, four helical ribsare provided that are spaced about 90° apart from one another on the circumference of the main body. The helical ribseach extend spirally upon the outer surfaceof the main bodywith a relatively large pitch (i.e., the end-to-end vertical rise of the helical ribs inis large compared to the horizontal run of the helical ribs along the helical path defined in the ribs). In the illustrated example, the pitch of the helical ribsis such that, from the base of the pile receiving endto the distal end of each rib, less than one complete turn of a helix is completed. For the context of the present description, a complete turn of a helix shall refer to a full 360° revolution on the circumference of the main body. As such, and in the exemplary coupler shown, each ribcompletes a fractional turn (i.e., less than one turn or less than a 360° revolution) of a helix on the main body.

In the illustrated example, each ribcompletes about a quarter turn (i.e., ¼ turn) of a helix on the main body, although more or less than about ¼ turn is possible in alternative embodiments. The distinct, helical ribsextend as thread-like members on the outer surface of the main body, but are specifically distinguished from a more conventional threaded connection including small pitch helical threads that continuously define multiple turns of a helix. While a specific geometry and a specific number of helical ribsis shown and described, it is appreciated that alternative numbers of ribsand/or alternative geometries of ribsis possible in another embodiment.

In the example shown, each ribincludes a first longitudinal side edgeand a second longitudinal side edgeopposing the first side edge. The first side longitudinal side edgeis uniformly curved without any discontinuity, while the second longitudinal side edgeincludes a discontinuous laterally extending projection. Such laterally extending projection on the longitudinal side edge, but not the longitudinal side edge, imparts an asymmetry to each rib. The laterally extending projection defines an anti-reverse rotation sectionhaving an increased lateral thickness than the remainder of each rib. The anti-reverse rotation sectionextends proximate to but is spaced from the retaining groovesdefined in each rib. The anti-reverse rotation sectionoverhangs the retaining grooveon the longitudinal side edge. The overhanging anti-reverse rotation section, in turn defines an anti-reverse rotation stop surfaceand an uplift bearing surface. The anti-reverse rotation stop surfacein the example shown extends along a helical path that is laterally offset from the remainder of the helical path of the second longitudinal side edge, while the uplift bearing surfaceextends perpendicularly to the longitudinal axial centerline of the coupler. In the illustration of, the longitudinal axial centerline of the couplerextends vertically while the uplift bearing surfaceextends horizontally in each rib. The uplift bearing surfacesextend planar to one another in the horizontal direction.

Since four ribsare provided in the coupler, four overhanging anti-reverse rotation sectionsare provided (one in each rib) that are distributed about the circumference of the coupler, four anti-reverse rotation stop surfacesare provided (one in each overhanging anti-reverse rotation section) that are distributed about the circumference of the coupler, and four uplift bearing surfacesare provided (one in each overhanging anti-reverse rotation section) that are distributed about the circumference of the coupler. The anti-reverse rotation stop surfacesand uplift bearing surfacesengage complementary features in the couplerto prevent relative rotation of the couplers in the reverse direction beyond a predetermined amount or degree and thereafter to maintain a full, rotational interlock of the couplers,in the reverse rotational direction, while simultaneously realizing an axial interlock of the couplers,via the uplift bearing surfaces in each coupler. As shown in the Figures, the overhanging section, the anti-reverse rotation stop surfaces, and the uplift bearing surfacesin each ribis integrally formed and built-in to the coupler design, and may be formed via known manufacturing processes such as, for example, casting, forging and swaging, and machining processes in combination with the remaining features of the coupler.

Referring to, helical groovesare formed to depend from the inner surfaceof the main bodyin the coupler. Each helical groovereceives a respective one of the helical ribs() when the coupleris mated with the coupler(). The helical groovesare shaped in a complementary manner to the helical ribsbut are larger than the helical ribs so as to permit a limited degree of rotational, side-to-side movement of the ribsin the grooves. As such, a rotational, side-to-side movement of the ribsin the groovesis intended as the couplers are installed but only to a certain extent in order to prevent an over-rotation of the couplers that could overload or overstress the spring elementand compromise the axial connection between the couplers. Specifically, and referring toeach grooveincludes a first longitudinal side edgeand a second longitudinal side edge. As best shown in, the longitudinal side edges,are spaced apart by a first circumferential distance that about twice as much than the circumferential spacing of the longitudinal side edges,of the ribsin the coupler. That is, and in the position shown in, the side edges of the groovesin the couplerare oversized relative to the side edges of the ribsin the coupler, and such oversizing means that the side edges of ribsare gapped from each of the side edges of the grooves. The ribsmay therefore be moved relative to the grooves(or vice versa) before engaging a rotationally interlocked position between the couplers,. As such, the couplers,may be rotated relative to one another within a predetermined limit defined by the gap length in both forward and reverse directions. Such a predetermined, limited degree of side-to-side movement of the ribswithin the gaps may be increased or decreased in various embodiments to provide more or less relative rotation of the couplers before becoming positively engaged in the forward or reverse direction of rotation as further described below.

As shown in, the first longitudinal side edgeof each grooveis uniformly curved without any discontinuity, while the second longitudinal side edgeincludes a discontinuous laterally extending projection. Such laterally extending projection on the longitudinal side edge, but not the longitudinal side edge, imparts an asymmetry to each groove. The laterally extending projection defines an anti-reverse rotation sectionproximate a distal end of the coupler. The anti-reverse rotation sectionextends proximate to but is spaced from the exterior retaining groovesdefined in the outer circumference of the coupler.

Since four ribsare provided in the coupler, four groovesare provided in the couplerthat are distributed about the circumference of the coupler. As shown in the Figures, the anti-reverse rotation sectionis integrally formed and built-in to the coupler design, and may be formed via known manufacturing processes such as, for example, casting, forging and swaging, and machining processes in combination with the remaining features of the coupler.

The anti-reverse rotation sectionconstricts the groovein the lateral direction, and when coupleris rotated in a reverse rotational direction (e.g., clockwise in) the anti-reverse rotation sectionof the respective groovesreceives the anti-reverse rotation sectionsof the ribs. Once the anti-reverse rotation sectionsof the ribsare so received, the anti-reverse rotation stop surfaceof the anti-reverse rotation sectionsengage the longitudinal side wallsof the grooves. Such engagement provides a positive stop to relative rotation of the couplers,and the couplers,will thereafter be rotationally interlocked if subjected to continued reverse rotation. The uplift bearing surfacesof the anti-reverse rotation sectionsalso respectively seat upon the surface of the anti-reverse rotation sectionwhen the anti-reverse rotation sectionsof the ribsare received by the anti-reverse rotation sectionin the respective grooves, establishing a positive axial interlock between the couplers if subjected to uplift forces. The spring elementis therefore mechanically isolated from undesirable mechanical loading associated with reverse rotation and uplift forces, preventing shear stress and possible failure of the spring elementthat could otherwise occur.

Likewise, when the coupleris rotated in a forward rotational direction (e.g., counter-clockwise in) the anti-reverse rotation sectionsof the respective groovesare disengaged from the anti-reverse rotation sectionsof the ribs, and the side edgesof the ribsengage the side edgesof the grooves. Such engagement provides a positive stop to relative rotation of the couplers,and the couplers,will thereafter be rotationally interlocked if subjected to continued forward rotation. Axial forces are also effectively distributed between the helical ribsand the grooves, establishing a positive axial interlock between the couplers when driven in the forward direction.