Patent Description:
The present technology relates to a thread-tapping fastener, and in particular a concrete fastener, and improvements to the installation thereof.

Thread-tapping concrete screws are screwed into holes drilled into a construction material, especially concrete, without the use of a plug. Normally, as the screw is being screwed in, the screw works its way into the construction material in such a way that the thread taps or cuts a mating thread into the construction material. Therefore, the screw itself cuts the thread or mating thread needed for the required positive fit between the thread and the construction material.

When the thread-tapping screw is being screwed into a drilled hole, stone powder from the construction material is formed in the area of the end of the screw. The stone powder can result from not being completely removed from the drilled hole after the hole was made and/or the stone powder is formed when the thread-tapping screw is being screwed into the drilled hole in the area of the end of the screw.

Over time, cracks may develop in installations of a fastener in concrete which can be repaired by adhesives and some fasteners have, in the past, been installed using adhesives.

<CIT> discloses a bolted connection for a recess in a ground that is delimited by an inside wall surface includes a bolt configured to be disposed in the recess.

<CIT> relates to a storage-stable hardener composition for a reaction resin based on a radically curable compound.

Described herein is a method for installing fastener in a base material, according to claim <NUM>. The fastener has a shank having a first end and a second end defining a length, a head provided at the second end, and a thread provided on the shank which includes a leading edge and a trailing edge adapted remove portions of the base material when inserted into the base material. The method includes forming a hole having a diameter which is the same as a nominal shank diameter of the fastener to be installed in the base material The hole is then filled with an adhesive having a viscosity of <NUM> cP or less using an injection gun. Finally, the fastener is rotated into the hole such that the adhesive is forced into portions of the base material adjacent to the shank and thread when the thread is fully inserted into the hole.

A fastening structure is also described, according to claim <NUM>. The structure includes a base material, a hole having a diameter which is the same as a nominal shank diameter of the fastener to be installed in the base material and a fastener in a bore in the base material. The fastener comprises a shank having a first end and a second end defining a length, a head provided at the second end and adjacent to a top surface of the base material, a thread provided on the shank which includes a leading edge and a trailing edge adapted remove portions of the base material when inserted into the base material, the thread embedded in the base material along a length of the bore. An adhesive having an installation viscosity of <NUM> cP or less provided into the bore using an injection gun is embedded into the base material adjacent to the walls of the bore and the embedded threads of the fastener.

Improvements in a method for installing fastener in a base material are described. The fastener has a shank with a a thread provided on the shank which includes a leading edge and a trailing edge adapted remove portions of the base material when inserted into the base material. The method includes forming a hole having a diameter which is a nominal shank diameter of the fastener to be installed in the base material. The hole is then filled with an adhesive having a viscosity of 350cP or less (not in line with the claimed invention) and in one embodiment <NUM> cP or less, and the fastener is rotated into the hole such that the adhesive is forced into portions of the base material adjacent to the shank and thread when the thread is fully inserted into the hole.

<FIG> illustrates a plan view of a concrete fastener <NUM> which may be installed into a pre-drilled drilled in concrete.

The fastener <NUM> has a fastener head comprising nut <NUM> and washer <NUM> at one end of a fastener shank <NUM>. A thread <NUM> is provided on the fastener shank <NUM>. Shank <NUM> has a section <NUM> that is configured without a thread <NUM>. The section <NUM> transitions to integral washer <NUM> and nut <NUM> at <NUM>. The shank <NUM> has a root or nominal diameter D2 of the fastener shank <NUM> as well as an outer diameter D1 on the thread <NUM>. The thread <NUM> also has a pitch P, which corresponds to the distance between any two windings of the thread <NUM>. The fastener <NUM> is inserted in a pre-drilled hole having a diameter matching or slightly larger than a shank of the fastener.

A front section 127a of the fastener <NUM> starts at the fastener end <NUM> and runs in the direction of a longitudinal axis CL of the fastener <NUM> towards the fastener head. The front section 127a in this embodiment encompasses approximately two windings of the thread <NUM>.

While the fastener <NUM> of <FIG> is suitable for use with the present technology, any of the fastener embodiments disclosed in<CIT>, inventor Joel Houck, may be utilized in accordance with the installation techniques described herein.

Embodiments of the fastener of Application Serial Number <CIT> may include: a fastener having a flat-topped thread; and/or a shank detent region; and/or a variable length shank detent region; and/or a fastener having a variable depth shank detent region; and/or a thread with a first thread angle in a region adjacent to the tip or leading end of the fastener and a second, smaller thread angle in a region between the first thread angle and the second end of the fastener and/or one or more flutes at the tip of the fastener; and/or a tri-obular thread; and/or a portion of the thread novel saw-tooth thread having a triangular leading edge followed by a shell-shaped trailing edge; and/or a dual lead thread at the tip of the fastener.

<FIG> illustrates a method for installing the fastener <NUM> of <FIG> or any of the fastener embodiments illustrated in Application Serial Number <CIT>. <FIG> will be described with reference to <FIG> which are partial, cutaway views illustrating the steps of a fastener installation method of <FIG>.

At step <NUM>, an installer will drill a bore <NUM> in the base material <NUM> using, for example, a Carbide drill bit, with the hole drilled to have the same diameter as the nominal diameter of the fastener to be installed. The bore <NUM> is drilled to a specified minimum hole depth to accommodate the fastener any thread tapping dust which is not removed by cleaning the bore. This is illustrated in <FIG> which illustrates the base material <NUM> having a bore <NUM> drilled therein by a drill bit <NUM> coupled to a drill chuck <NUM>.

At <NUM>, the hole is clean using, for example, compressed air. This is illustrated in <FIG> which shows a portion of the compressed air canister <NUM> having a cannula delivering forced are into the bore to blow particulate out of the bore <NUM>. Alternatively, or in addition to step <NUM>, the bore <NUM> can be drilled deep enough to accommodate the fastener depth and any dust which results in drilling and tapping without the forced air cleaning at <NUM>. At <NUM>, and as illustrated in <FIG>, a brush <NUM> may be utilized to further clean the bole <NUM> such as, for example, by rotating the bus back and forth within the bore <NUM>. At <NUM>, the fastener <NUM> is inserted through a fixture <NUM> and into the bore <NUM>. The fasteners is then tightened into the base material using a powered fastening tool at step <NUM> as illustrated in <FIG>. At <NUM>, the fastener is tightened into the base material <NUM> until the washer head portion of the fastener contacts the fixture <NUM> as illustrated in <FIG>.

<FIG> shows four cross-sectional views of fastener <NUM> illustrating the pull-out effect on a cracked concrete substrate when the fastener has an angled top surface t four stages (labeled <NUM> through <NUM> in each <FIG> illustrating the effect of pullout forces on the embodiments of fasteners disclosed in <FIG> over time.

At stage <NUM> of <FIG>, the fastener <NUM> is at rest in a concrete slab, having been installed in the pre-drilled hole. A crack has formed in the concrete due to external forces acting on the concrete, and the crack has intersected the fastener location. As a pull-out force <NUM> is exerted on the fasteners at stage <NUM> in <FIG>, lateral forces <NUM> are exerted by external forces acting on the concrete, causing some separation in the concrete slab away from the fastener. At this stage the angle on the top of the thread along with the pullout force on the fastener causes the fastener to slip upwards in the hole. As illustrated at stage <NUM>, the removal of the external load along with the elasticity of reinforcing bars embedded in the concrete will cause the concrete to move back toward the fastener as the pull out force <NUM> remains constant. Because the fastener has already slipped up in the hole, the concrete is crushed slightly at the top of the thread as the concrete returns to its original position. Note that at stage <NUM> of <FIG>, some separation <NUM> begins to occur between the thread groove in the concrete slab and the thread of the fastener, loosening the strength of the fastener in the slab. Over time, this results in an enlarged separation <NUM> as shown at stage <NUM> of <FIG>.

The technology of the present disclosure helps increase the resistance to pull out described with respect to <FIG>.

<FIG> illustrates a method for installing the fastener <NUM> of <FIG> or any of the fastener embodiments illustrated in Application Serial Number <CIT> in accordance with the present technology. <FIG> will be described with reference to <FIG>, and <FIG> which are partial, cutaway views illustrating the steps of a fastener installation method of <FIG>.

In the method of <FIG>, steps <NUM>, <NUM> and <NUM> are performed in the same manner as described above and as illustrated in <FIG>. Prior to installing the fastener in the bore, at <NUM>, a quantity of low-viscosity adhesive is applied into the bore. In one embodiment, the adhesive may comprise low-viscosity structural injection epoxy having a viscosity of <NUM> cP or less. For example, a two-component, high-modulus, high-solids, moisture-tolerant epoxy designed for pressure injection, gravity feeding and flood coat filling of concrete cracks such as CI-LV Low-Viscosity Injection Epoxy having a viscosity of <NUM> cP available from Simpson Strong-Tie was found effective in performing the installation method disclosed herein. In another embodiment, CI-SLV Super-Low-Viscosity Injection Epoxy having a viscosity of 150cP, also available from Simpson Strong-Tie, may be utilized. As illustrated in <FIG>, the adhesive may be injected into bore <NUM> using an injection gun <NUM>.

Next, at <NUM>, the fastener <NUM> is inserted into the bore having the adhesive therein and tightened at <NUM> within the gel-time specified for the adhesive. A typical gel-time for such an adhesive is approximately <NUM> minutes. During the tightening process, some adhesive may extrude from the bore and at <NUM>, the excess adhesive should be removed. At <NUM>, the adhesive should be allowed to cure before applying a load to the fixture <NUM> fastened by the fastener <NUM>.

The resulting structure has a portion <NUM> of the adhesive lining the bore. As illustrated in <FIG>, some adhesive may penetrate the concrete walls at the bottom of the bore and adjacent to the walls of the bore. Normally, the low-viscosity adhesives described herein are utilized for injection into of cracks in structural concrete, as the low-viscosity epoxy is suitable for repair of hairline cracks (<NUM>") and cracks up to <NUM>/<NUM>" (<NUM>) in width. When the fastener is installed using the low-viscosity adhesive in the disclosed method, the displaced adhesive is forced up against the walls of the bore <NUM> where it can seep into the concrete, reinforcing the surface where the fastener threads are engaged. When the crack opens and closes in the concrete, the surface that rubs against the threads is much harder than the bare concrete, so there is less crushing of the concrete. This results in much higher performance in this condition than without the adhesive as illustrated in the below graphs.

Alternative adhesives may be utilized in accordance with the method and the amount of seepage or penetration of the adhesive into the concrete varies with the composition of the adhesive. As such, there are three possible conditions for the adhesive in the bore based on the viscosity; most or all of the adhesive seeps into the concrete with the remainder filling some of the annular space between the screw shank and the concrete; the adhesive fills the annular space between the fastener and the concrete with some seeping into the concrete to reinforce it; and the adhesive fills the annular space between the screw shank and the concrete with none seeping into the concrete. Testing results on different fasteners, some of which are described below, found that a <NUM> cP adhesive used in the disclosed method performed better than a <NUM> cP adhesive, though the <NUM> cP adhesive nevertheless improved pull-out performance over fasteners installed without using the method. Adhesives with viscosities even less than <NUM> cP can also be utilized in the method.

<FIG> and <FIG> are crack cycling graphs of the displacement of a fastener which result from testing various methods of installation on the fastener of <FIG> using an adhesive with a <NUM> cP viscosity. <FIG> illustrates displacement of a fastener over a number of stress cycles where a fastener <NUM> is installed using the method of <FIG> where no adhesive was used during installation. <FIG> illustrates displacement of a fastener installed where low-viscosity adhesive was used during installation (the method of <FIG>).

As illustrated in <FIG>, the displacement of the fastener ramps up quickly in as few as <NUM> - <NUM> cycles in certain tests. Using the method of <FIG>, displacement is less than <NUM> inch even after hundreds of cycles.

Embodiments of the fastener are suitable for insertion into a concrete material having a pre-formed bore of sufficient diameter to accommodate a diameter of the shank and for forming a self-threaded grooves in the bore in the concreate material.

<FIG> illustrates a comparison of the displacement of a fastener such as that disclosed in Application Serial Number<CIT>, <FIG> thereof, where the top edge of the thread of the fastener has a flat top edge (M8) versus fastener <NUM> (M3). The graph illustrates the displacement for fasteners during a stepwise crack cycling test where the installation comprised: fastener <NUM> using the method of <FIG> with a <NUM>% total force ("M3 <NUM>%"); fastener <NUM> using the method of <FIG> with a <NUM>% total force ("M3 w/SLV <NUM>%"); fastener <NUM> using the method of <FIG> with a <NUM>% total force ("M3 w/SLV <NUM>%"); fastener <NUM> using the method of <FIG> with a <NUM>% total force ("M3 w/SLV <NUM>%"); fastener <NUM> using the method of <FIG> with a <NUM>% total force without brushing the bore ("M3 w/SLV <NUM>% no brush"); and fastener of Application Serial Number <CIT> using the method of <FIG> with a <NUM>% total force and not brush cleaning ("M8 w/SLV <NUM>% no brush"). As illustrate in <FIG>, even without cleaning the bore, the adhesive installation method disclosed herein provides improved resistance to displacement over prior installation methods and substantially improves the performance of numerous types of concrete fasteners.

All such embodiments of fasteners discussed herein benefit from the use of the installation methods described herein.

Claim 1:
A method for installing fastener (<NUM>) in a base material (<NUM>), the fastener (<NUM>) comprising a shank (<NUM>) having a first end and a second end defining a length, a head provided at the second end, a thread (<NUM>) provided on the shank (<NUM>) which includes a leading edge and a trailing edge adapted remove portions of the base material (<NUM>) when inserted into the base material (<NUM>), the method comprising:
forming a hole having a diameter which is the same as a nominal shank (<NUM>) diameter of the fastener (<NUM>) to be installed in the base material (<NUM>);
filling the hole with an adhesive having a viscosity of <NUM> cP or less using an injection gun;
causing the fastener (<NUM>) to be rotated into the hole such that the adhesive is forced into portions of the base material (<NUM>) adjacent to the shank (<NUM>) and thread (<NUM>) when the thread (<NUM>) is fully inserted into the hole.