text: the purpose of this new non - slip expansion anchor concept is to provide an improved anchor design capable of achieving superior performance over convention al type expansion anchors presently offered . another area to be considered is that of the effect of vibratory loading on the anchor performance . this is relevant considering the anchor is designed to provide minimal relaxation of the anchor assembly after installation . in conventional expansion anchors the bolt tends to loosen after the initial setting torque has been applied and as a result it must be re - tightened to establish the proper clamping load . the positive set between the anchor bolt and clip segments will provide minimal slip or creep once the anchor is set and the load is applied to the anchor . fig1 a and 1b illustrate a non - slip wedge anchor 10 in accordance with the present invention which is shown respectively in at rest and installed positions thereof . in fig1 c , the anchor 10 is seen from its underside . the anchor 10 includes an expander member 12 and an expansion member 14 . the expander member 12 is designed to be inserted in a hole h defined in a support structure s , such as a concrete element , and comprises a treaded section 16 adapted to extend in the hole h while having a proximal end 18 which extends outside of the hole h such as to be engaged by a threaded female member , such as a nut n , with a washer w being herein shown between the nut n and the support structure s . typically , an object , although not herein shown , is held by the anchor 10 to the support structure s ; it is noted that , in the present embodiment , as well as in the other embodiments of the various anchors herein shown and described , such an object has not been illustrated . the expander member 12 also includes a flared distal end 20 around which is provided the expansion member 14 which is dimensioned to frictionally engage the walls of the hole . once the anchor 10 has been introduced in the hole h , the nut n is rotated to displace the expander member 12 translationally outwardly of the hole h , as the friction forces between the expansion member 14 and the hole h are sufficient for it to remain stationary therein during the displacement of the expander member 12 , the flared end 20 of the expander member 12 causes the expansion member to expand , as seen in fig1 b , thereby anchoring the anchor 10 in the hole h . the expansion member includes a double - layered , folded over , proximal or trailing end 22 which defines an internal abutment shoulder 24 which can be engaged by an enlarged annular flange 26 provided distally of the flared end 20 of the expander member 12 . in fig2 a and 2b , a second wedge anchor 30 in accordance with present invention is illustrated and which comprises an expander member 32 ( shown in detail in fig3 a and 3b ) and an expansion member 34 ( shown in detail in fig3 c to 3 e ), or expandable clip . the expander member 32 is similar to the expander member of fig1 a in that it includes a treaded section 36 , having a proximal end 38 , a leading flared end 40 and a reduced diameter intermediate cylindrical section 42 therebetween . a shoulder 44 is defined at a junction of the intermediate and threaded sections 42 and 36 . the expansion member 34 comprises a leading support 46 , an expandable collar 48 and a leg 50 connecting the support 46 and collar 48 together . the collar 48 is split at 52 to allow it to expand , as seen in fig2 b , and defines thereat mating tongue and groove elements 54 and 56 , respectively . as seen in fig2 a and 2b , the leg 50 of the expansion member 34 is held captive in a groove 58 defined longitudinally in the flared end 40 ( see fig3 a and 3b ) thereby preventing the expansion member 34 from rotating with respect to the expander member 32 and forcing it to work vertically without twisting . in operation , the rotation of the nut n causes the expander member 32 to displace longitudinally and outwardly along the hole h . as the collar 48 of the expansion member 34 frictionally engages the walls of the hole h , it remains stationary therein while the groove 58 slides along the leg 50 . it is noted that the leg 50 is biased outwardly , i . e . to an open or deployed position , to ensure the initial frictional engagement of the collar 48 with the walls of the hole h . it is also noted that the outside surface of the collar 48 is knurled for additional friction . the partial withdrawal of the expander member 32 from the hole h causes the flared end 40 to expand outwardly the collar 48 with a trailing edge 60 of the collar 48 engaging the walls of the hole h at an angle with respect to a longitudinal axis of the hole h ( see fig2 b ). such an engagement with the hole h at a trailing end of the expandable member 34 , and with an angle opposed to that of the flared end 40 , is very secure and increases the force required to pull out the expanded anchor 30 from the support structure s . it is noted that the cylindrical intermediate section 42 allows the collar 48 to be received in a collapsed position ( see fig2 a ) when the anchor 30 is initially driven in the hole h . also , the shoulder 44 prevents the expandable member 34 from moving up on the threaded section 36 of the expander member 32 . the tongue and groove elements 54 and 56 align the collar 48 at its split 52 to provide a peripheral , 360 °- like , gripping of the expandable member 34 into the walls of the hole h . the expandable member 34 is also provided on its leg 50 with a reinforcement rib 62 to provide more rigidity to the leg 50 . the leading support 46 of the expandable member 34 comprises a concave bottom 64 to still give more rigidity to the leg 50 . at the very end of the flared section 40 of the expander member 32 is a radial flat section land 66 to allow for maximum interference between the hole h , the expander member 32 and the expansion member 34 . in the following descriptions which pertain to variants of the anchor 30 of fig2 a and 2b , components which are identical in function and in structure to corresponding components of the anchor 30 bear the same references as in fig2 a to 3 e , whereas similar parts have been attributed suffixes to their reference numerals with respect to the numerals used in fig2 a to 3 e . any components which are new to the anchors of the following variants are identified by new reference numerals . in fig4 a to 5 e and 6 a to 7 e , third and fourth wedge anchors 70 and 80 , respectively , also in accordance with present invention are illustrated . these anchors 70 and 80 are very similar to the anchor 30 , except that their respective expansion members 34 a and 34 b have respectively 2 and 3 legs 50 a and 50 b , respectively , as opposed to the single leg 50 embodied in the expansion member 34 of anchor 30 . the multiple splits 52 b result in that the collar 48 b includes three clip segments . the expansion member 34 b of anchor 80 defines a pair of rounded radii 82 and 84 to increase the rigidity of the legs 50 b . therefore , with respect to the anchor of fig6 a to 7 e , the new wedge concept is made up of two components . one is a specially formed stud or expander member which is partially threaded at one end . assembled to the bottom end is a multi segment expansion clip or expansion member which is assembled to the flared end of the stud opposite the threaded end . the stud ( fig7 a and 7b ) is made of high strength steel which can be heat treated for heavy duty applications . the stud is unique in that it contains a number of features unlike conventional wedge type anchors . the stud is comprised of an external thread at one end which has a reduced diameter at the bottom end of the thread which engages the multi segmented clip . the difference in diameter prevents the clip from travelling upward onto the threads of the bolt . the end of the bolt opposite to the thread end has a flared section extending outward . the end of the flare incorporates several guide segments used to maintain the position of the expansion member as it expands during installation and is also used to prevent rotation of the total clip itself . at the very end of the flared section of the bolt is a radial flat section land to allow for maximum interference between the hole , stud and expansion clip . the expansion clip ( fig7 c to 7 e ) is made of high strength steel and is comprised of three formed segments which are pre - expanded prior to assembly . each of the segments compresses against the hole in the concrete when driven into the hole providing frictional resistance to axial pullout during installation and after the load is applied . each segment is connected to a formed concave shaped section via a formed leg section . each leg connecting a segment has a strengthening rib and internal radii to add rigidity to the clip assembly . another feature located on each segment is a locking tab which helps control expansion and keep the clip segments in line . this provides for a full 360 degree expansion . a portion of each is knurled to provide additional friction and holding power . a nut / washer is assembled to the threaded end of the stud assembly . the embedment is determined and measured from directly under the washer to the bottom end of the bolt . the anchor is driven into a pre - drilled hole in the concrete . as the anchor is driven into the hole using a hammer , the pre - expanded segments of the clip assembly provide the frictional resistance to resist the axial pullout resulting during the initial setting of the anchor . as the installation torque is increased , the nut is tightened flush against the flat washer and the concrete . as a result the tapered portion at the bottom of the stud is pulled upward into the clip segments causing expansion of the lower clip segments located toward the bottom portion of the bolt ( see fig6 b ). the constant outward force provided by the upper section of the segments cause the clip segments to dig into or interfere with the concrete thus preventing the clip assembly from sliding or creeping upward which causes the bolt to loosen in the hole of the concrete . once the installation torque is reached , the load can be applied to the bolt . the purpose of this undercut type anchor concept is to provide a high strength instant holding mechanical type anchor designed to achieve superior pullout performance in concrete while provided a positive lock into the concrete to prevent anchor slip or creep . the feature of being instant holding makes it suitable for applications needing to apply the load immediately which is not the case with chemical type anchors . this anchor must be capable of withstanding both vibratory and shock type loads without failure . failure would be determined by the improved load versus displacement relationship . fig8 a and 8b illustrate an undercut wedge anchor 100 in accordance with the present invention which is shown respectively in first and second positions thereof in a support . the undercut anchor 100 consists of two specially formed components , namely a stud or expander member 102 and a clip or expansion member 104 , both made of high strength steel to provide the resistance needed to overcome the forces acting as a result of the high installation torque required to set the anchor into the concrete . existing designs consist of more than two assembled components . the expander member 102 which is made of high strength steel to resist heavy duty tension and shear applications comprises a threaded section 106 , a proximal hex drive element 108 located at the top or beginning of the threaded section as a positive means of providing the spinning or rotational action to the anchor 100 during installation . the standard hex element 108 allows the use of a conventional type socket type drive for fast access and easy removal . at the opposite end of the expander member 102 is a specially designed stud configuration that provides a means to expand the undercut mechanism ( or expansion member 104 ) which will provide the positive lock between the expander member 102 and the concrete of the support structure s . this stud configuration consists of longitudinal opposed first leading and second trailing flared portions 110 and 112 , respectively . the trailing tapered portion 112 , located towards the threaded section 106 , provides a means of expanding the undercut mechanism or expansion member 104 which in turn defines the undercut into the concrete . at a proximal end of the trailing flared portion 112 , is a collar 114 which is used to prevent the undercut mechanism or expansion member 104 from moving onto the threaded section 106 of the expander member 102 . the leading flared portion 110 provides a means of expanding the bottom portion , or distal end , of the expansion member 104 , to thus complete the undercut / locking process . at the end of each flared portion is a specially formed configuration to prevent the expansion member 104 from rotating free of the expander member 102 during the initial undercut action and during the final installation process . the multiple function specially designed undercut mechanism / expansion member 104 which is made of high strength steel comprises an expandable collar 116 , a leading support 118 and a pair of legs 120 , reinforced with ribs 122 , connecting the expandable collar 116 and the leading support 118 together . the leading support 118 has a formed end 124 at the bottom to reduce friction and serve as a means of providing a way of forcing the expandable collar 116 against the trailing flared portion 112 of the expander member 102 . the expandable collar 116 is split at 126 to allow it to expand and has at its trailing end a pair of inwardly directed tabs 128 which with the legs 120 engage trailing and leading recesses 130 and 132 , respectively , defined in the trailing and leading flared portions 112 and 110 . the expansion member 104 is held captive by these longitudinal recesses 130 and 132 thereby preventing the expansion member 104 from rotating with respect to the expander member 102 and forcing it to work vertically without twisting . the expandable collar 116 defines opposed leading and trailing edges 134 and 136 , respectively . between the flared portions 110 and 112 , the expander member 102 defines a cylindrical portion 138 which allows the expandable collar 116 to be received in a collapsed position when the anchor 100 is initially driven in the hole h . the anchor 100 is driven into the pre - drilled hole h until it is reaches its bottom ( see fig8 a ). a rotary drill with a hex drive socket attached is assembled to the external hex drive element 108 . to facilitate the undercut action , the installer forces the expander member 102 down by applying constant downward pressure thereon while it is spinning . once the expansion member 104 is frictionally engaged to the walls of the hole h , the further downward displacement of the expander member 102 causes the trailing flared section 112 to engage the expansion member 104 and forces the latter to expand radially outward ( see fig8 a ), such that the rotation of the expander member 102 resulting from it being connected to the rotary drill causes the expansion member 104 to rotate ( as it connected at its tabs 128 and legs 120 to the trailing and leading recesses 130 and 132 of the expander member 102 ). the spinning of the expansion member 104 causes its trailing edge 136 to cut into the support structure s ( e . g . of concrete ), thus providing the initial undercut action . once the undercut action has been completed , the expander member 102 is set by assembling the nut n and washer w to a trailing end of its threaded section 106 . the nut n is rotated until it is hand tight against the flat washer w and flush with the support structure s . as the nut n is tightened to a specified torque , it draws the expander member 32 longitudinally and outwardly out of the hole h . although the trailing flared portion 112 disengages from the collar 116 , the trailing edge 136 of the collar 116 remains set in the undercut ( see fig8 b ) in view of its memory , for instance resulting from the trailing edge 136 having been plastically deformed . as the expandable collar 116 remains stationary by virtue of the positive locking engagement of its trailing edge 136 with the walls of the hole h , the leading flared portion 110 causes the leading end of the collar 116 to expand outwardly ( see fig8 b ). the expansion member 104 is prevented from rotating by its legs 120 being laterally confined in the recesses 132 and being thus limited to relative longitudinal displacement therein . it is noted that the expandable collar 116 may be spring loaded or biased outwardly , i . e . to a partly open or deployed position , to ensure the initial frictional engagement thereof with the walls of the hole h . the partial withdrawal of the expander member 102 from the hole h thus causes the leading flared portion 110 to expand the collar 116 outwardly with the leading edge 134 of the collar 116 engaging the walls of the hole h ( see fig8 b ) thereby completing the setting of the undercut mechanism / expansion member 104 . the anchor 100 thus provides the undercut needed to maintain the locked position of the installed anchor 100 . the upper portion of the expansion member 104 also contains a special configuration which includes a formed cutting edge 136 and / or surface to allow it to cut into the concrete and aggregate via the axial rotation provided by the drive tool spinning the expander member 102 . to increase resistance to wear , a special coating ( e . g . abrasive , diamond coatings ) or a series of hardened particles 140 can be applied onto the surface and / or cutting edge 136 of the undercut portion of the expansion member 104 . the hex drive element 108 can take other forms as long as the expander member 102 can be gripped from outside the hole h and rotated . fig1 a to 10 d , 11 a to 11 c , 12 a to 12 c and 13 a to 13 c show four variants of the undercut wedge anchor 100 wherein the expansion member 104 of fig9 e to 9 g has been modified , for instance at its formed end 114 and tabs 128 ( with similar adjustments to the trailing recesses 130 ). in the present non - slip wedge anchors ( see fig1 to 7 ) and undercut wedge anchors ( see fig8 to 13 ), the expansion of the expansion member ( see , for instance , fig7 c of the non - slip wedge anchor and fig8 b and 9e of the undercut wedge anchor ) results from that at least proximal or trailing edge thereof , i . e . and upper section of the expandable segments thereof , bites into or interferes with the peripheral concrete wall of a receiving hole thereby preventing the assembly from sliding or creeping upwards and cause the bolt to loosen in the hole defined in the concrete structure . this prevents axial removal of the anchor from the hole . by so expanding the expansion member , resistance to axial pullout is improved . the resiliency of the expansion member allows the anchor to be easily inserted in the hole while urging the same against the wall of the hole to prevent the expansion member from rotating as a torque is applied to a nut engaged to the bolt . the rotation of the nut causes the bolt to move translationally outwardly of the hole and thus causes a flared expander portion of the bolt to move axially into the stationary expansion member to expand the expansion member as per the way described hereinbefore . with respect to the non - slip wedge anchor , this is well illustrated in fig6 b , and in the case of the undercut wedge anchor , this is well shown in fig8 b . in the case of the undercut wedge , there is a first expansion of the expansion member followed by a rotation of the bolt such that the expanded upper edge of the expansion member cuts into 360 ° of concrete and thus provides the undercut needed to maintain the locked position of the anchor . more specifically , the first expansion of the expansion member is effected by applying a constant downward pressure on the bolt so as to cause the expansion to move axially over an upper flared portion of the bolt . once the undercut action has been completed , the expansion member is expanded by drawing a lower flared portion of the bolt into the expansion member via operation of a nut threadably engaged with the threaded end of the bolt , thereby completing the setting of the undercut / expansion mechanism . a main advantage of the above - described non - slip and undercut wedge anchors resides in the fact that they provide a much stronger grip than that of known friction - based sleeve designs . in the case of the undercut wedge anchor , no separate drill bit is required to define the undercut . fig1 a illustrates a spiral wedge anchor 200 having a stud or expander member 202 defining a spiral and tapered lower end 204 for receiving a resilient coil or expansion member 206 ( e . g . made of hard steel ) which , in view of the initial frictional engagement of the coil 206 with the wall of the hole h in the support structure s , climbs along the tapers of the lower stud end 204 as the stud 202 is pulled rotatably outwardly of the hole h , whereby the coil 206 is expanded outwardly radially for further contacting the hole h ( as seen in fig1 ), being firmly wedged between the concrete s and the stud 202 . an object o can thus be firmly held to the support structure s . when referring throughout this disclosure and claims to terms such as “ withdraw ”, it is readily understood that the expander member is not completely removed from the hole , but rather partly displaced longitudinally out of the hole and relative to the expansion member for effecting the expansion of the expansion member . the anchored position of the present anchors well illustrate this configuration ( see fig1 b , 2 b , 4 b , 6 b , 8 b and 15 ).