U.S. patent application number 13/907473 was filed with the patent office on 2014-12-04 for wedge anchor bolt.
The applicant listed for this patent is Climb Tech, LLC.. Invention is credited to Ivan A.J. Kekahuna, Eric Shawn Patrick.
Application Number | 20140356077 13/907473 |
Document ID | / |
Family ID | 51059588 |
Filed Date | 2014-12-04 |
United States Patent
Application |
20140356077 |
Kind Code |
A1 |
Kekahuna; Ivan A.J. ; et
al. |
December 4, 2014 |
WEDGE ANCHOR BOLT
Abstract
A wedge anchor bolt having a screw member, a wedge member, and a
cage member. The bolt is anchored into a drilled hole by wedging
the wedge member in the end of the cage member by turning the screw
member, with the result being that the wedge member becomes stuck
in the cage member. For ejecting the wedge member from the cavity
the screw member includes at least one of (1) one or more depressed
portions, and (2) one or more projecting portions, defining a step,
and the cage member includes one or more corresponding
step-engaging portions for making an interference contact with the
step, so that further withdrawal of the threads ceases to withdraw
the threads relative to the cage member while continuing to
withdraw the threads relative to the wedge member, thereby forcing
the wedge member distally relative to the cavity.
Inventors: |
Kekahuna; Ivan A.J.;
(Austin, TX) ; Patrick; Eric Shawn; (Austin,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Climb Tech, LLC. |
Austin |
TX |
US |
|
|
Family ID: |
51059588 |
Appl. No.: |
13/907473 |
Filed: |
May 31, 2013 |
Current U.S.
Class: |
405/259.4 |
Current CPC
Class: |
A63B 29/024 20130101;
A62B 35/0068 20130101; E04B 1/4157 20130101; F16B 13/066 20130101;
E04G 21/3276 20130101 |
Class at
Publication: |
405/259.4 |
International
Class: |
E04B 1/41 20060101
E04B001/41 |
Claims
1. An anchor bolt, comprising: a screw member having a head
defining a proximal end of the screw member, and an elongate shank
extending from the head and terminating at a distal end of the
screw member, the shank having a threaded end, the head being or
having a feature shaped for coupling with a tool so as to render
the tool capable of turning the head about an elongate axis of the
screw member, thereby either axially advancing or axially
withdrawing the threads of the threaded shank; a wedge member
threadably engaged by the threaded portion of the shank; and a cage
member defining a cavity through which the threaded end of the
shank extends and into which at least a portion of the threadably
engaged wedge member is allowed to penetrate, the wedge member
being shaped in cooperation with the cavity to force the cavity to
undergo a radial expansion as a result of being drawn into the
cavity by means of advancing the threads of the threaded shank, the
wedge member becoming stuck in the cavity as a result, wherein, for
ejecting the wedge member from the cavity, the screw member
includes at least one of (1) one or more depressed portions, and
(2) one or more projecting portions, defining a step of abruptly
increasing radial dimension of the screw, and wherein the cage
member includes one or more corresponding step-engaging portions
for making an interference contact with said step when the threads
have been withdrawn from the cage and wedge members a sufficient
amount, so that further withdrawal of the threads ceases to
withdraw the threads relative to the cage member while continuing
to withdraw the threads relative to the wedge member, thereby
forcing the wedge member distally relative to the cavity.
2. The anchor bolt of claim 1, limited to one or more depressed
portions for defining said step.
3. The anchor bolt of claim 2, wherein said one or more depressed
portions is a necked-down portion of the screw member.
4. The anchor bolt of claim 3, wherein said necked-down portion is
substantially cylindrical.
5. The anchor bolt of claim 4, wherein each of said one or more
step engaging portions is or includes a tang depending from the
cage member.
6. The anchor bolt of claim 3, wherein each of said one or more
step engaging portions is or includes a tang depending from the
cage member.
7. The anchor bolt of claim 2, wherein each of said one or more
step engaging portions is or includes a tang depending from the
cage member.
8. The anchor bolt of claim 1, wherein each of said one or more
step engaging portions is or includes a tang depending from the
cage member.
9. The anchor bolt of claim 1, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
10. The anchor bolt of claim 9, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
11. The anchor bolt of claim 8, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
12. The anchor bolt of claim 7, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
13. The anchor bolt of claim 6, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
14. The anchor bolt of claim 5, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
15. The anchor bolt of claim 4, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
16. The anchor bolt of claim 3, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
17. The anchor bolt of claim 2, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
18. The anchor bolt of claim 1, further comprising a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
19. A method for removing an anchor bolt from a hole, the anchor
bolt including a screw member having a threaded end and defining a
screw axis, a wedge member into which the threads of the threaded
end of the screw member are threadably engaged, and a cage member
defining a cavity through which the threaded end of the screw
member extends and into which at least a portion of the threadably
engaged wedge member is allowed to penetrate, the anchor bolt
having been inserted into the hole in a first axial direction
parallel to the screw axis, the wedge member being shaped in
cooperation with the cavity to force the cavity to undergo an
expansion in one or more directions perpendicular to the screw axis
as a result of being drawn into the cavity by means of turning the
screw so as to advance the threads of the threaded end, the anchor
bolt being thereby wedged in the hole with the wedge member stuck
in the cavity, wherein, for ejecting the wedge member from the
cavity, the method comprises: turning the screw member in a first
radial direction for withdrawing the threads from the wedge member,
thereby causing the screw member to translate relative to the cage
member in a second axial direction opposite the first axial
direction; and stopping the screw member from further axial
translation relative to the cage member in the second axial
direction while allowing for continued turning of the screw member
in the first radial direction, so that further withdrawal of the
threads from the wedge member will result in forcing the wedge
member in the first axial direction relative to the cavity.
20. The method of claim 19, further comprising, during said step of
stopping, continuing to turn the screw in the first radial
direction and thereby continuing to withdraw the threads from the
wedge member, thereby resulting in forcing the wedge member in the
first axial direction relative to the cavity.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to low cost wedge anchor bolts
of the type commonly used to mount metal structures to
concrete.
BACKGROUND
[0002] An example is shown in FIG. 1. A low cost wedge anchor bolt
2 has a screw 4 with a screw-head 4a and a shank 4b. An expandable
cage 6 is coaxially disposed around the shank 4b, and the shank 4b
has a threaded end for engaging the internal threads of a wedge 8
at the distal end of the shank. An insertion portion 9 of the bolt
2, defined by the shank 4b, cage 6, and wedge 8, is inserted into a
drilled hole in the structure to which the anchor bolt is to be
anchored.
[0003] Turning the screw 4 in one direction, typically clockwise,
threads the shank 4b further into the wedge 8, drawing the wedge
into the cage 6 and thereby causing the cage to expand. Continuing
to turn the screw in the same direction eventually results in the
cage 6 being expanded sufficiently tightly against the interior
surface(s) of the hole to result in a frictional anchoring of the
insertion portion 9 therein.
[0004] Low cost wedge anchor bolts like that shown in FIG. 1 can be
used to provide fall protection for construction workers
constructing buildings formed of concrete walls, floors, or
ceilings. For that purpose a piece of "bolt attachment" hardware is
provided (not shown in FIG. 2) allowing for a worker's connection
with the anchor bolt. Typically, the bolt attachment hardware is a
plate having two through-apertures, one through which the screw 4
extends, for capturing and thus securing the bolt attachment
hardware behind the screw-head and the wall (or ceiling, or other
surface) into which the hole is drilled, and the other for allowing
the user to connect with the anchor bolt via a clip known as a
"carabiner." Typically, the worker is wearing a harness and the
harness is connected with the bolt attachment hardware via a
lanyard having a carabiner at each end, one for connecting to the
harness and one for connecting to the bolt attachment hardware.
[0005] Low cost wedge anchor bolts used in providing fall
protection for construction workers are generally not needed after
construction is complete. Moreover, to maintain the low cost, the
components of the basic wedge anchor bolt are typically formed of
ordinary steel and are thus susceptible to corrosion. So it is
often desirable, and it is often otherwise required by local
building codes, to remove them after construction is complete,
because corrosion of the bolt will weaken the surrounding concrete,
thus weakening the structure.
[0006] The problem is that the low cost wedge anchor bolt is not
easily removable. Once the bolt is tightened, the cage 6 and wedge
8 become, together, stuck in the hole, and there is no mechanism
provided for separating them. Thus while turning the screw in the
opposite direction allows for withdrawing the screw 4 from the
hole, the cage 6 and the wedge 8 will typically remain behind,
requiring another drilling step to drill these parts out of the
hole so that complete removal of the anchor bolt can be
accomplished.
[0007] "Expansion" type anchor bolts have been provided in the
prior art that are easily removable. Examples are those described
in U.S. Pat. Nos. 7,357,363 and 8,353,653. A comparison of these
with the anchor bolt 2 shows the "expansion" type to be a species
of wedge anchor bolt, but with significant adaptations providing
for ease of removability. For example, in the typical expansion
type anchor bolt, the cage is formed of one or more spoons
suspended by flexible rods or filaments; the wedge is spring-biased
to wedge the spoons against the interior surfaces of the hole; a
slidable bushing is provided for transmitting a hammering force
applied to the bushing to the wedge for knocking the wedge out of
its stuck position, placing the bolt in a relaxed configuration in
which the bolt becomes loose in the hole; and a means is provided
for remotely pulling the wedge relative to the spoons against the
spring-bias to allow the bolt to maintain the relaxed configuration
as the bolt is pulled out from the hole.
[0008] These adaptations have resulted in the cost of expansion
type anchor bolts being significantly higher than that of basic,
low cost wedge anchor bolts like that shown in FIG. 1, to the
extent that, even with the additional drilling step, the low cost
wedge type anchor bolt is the least costly alternative.
[0009] Accordingly there is a need for a basic wedge anchor bolt,
i.e., a wedge anchor bolt that is cost competitive with the bolt 2
shown in FIG. 1, which provides an ease of removability that has
heretofore only been available in the relatively expensive
"expansion" type anchor bolts.
SUMMARY
[0010] Disclosed is an easily removable low cost wedge anchor bolt.
The anchor bolt includes a screw member, a wedge member, and a cage
member. The screw member has a head defining a proximal end of the
screw member, and an elongate shank extending from the head and
terminating at a distal end of the screw member. The shank has a
threaded end, the head being or having a feature shaped for
coupling with a tool so as to render the tool capable of turning
the head about an elongate axis of the screw member, thereby either
axially advancing or axially withdrawing the threads of the
threaded shank. The wedge member is threadably engaged by the
threaded portion of the shank. The cage member defines a cavity
through which the threaded end of the shank extends and into which
at least a portion of the threadably engaged wedge member is
allowed to non-forcibly penetrate. The wedge member is shaped in
cooperation with the cavity to force the cavity to undergo a radial
expansion as a result of being drawn into the cavity by means of
advancing the threads of the threaded shank, the wedge member
becoming stuck in the cavity as a result.
[0011] For ejecting the wedge member from the cavity according to
the invention, the screw member includes at least one of (1) one or
more depressed portions, and (2) one or more projecting portions,
defining a step of abruptly increasing radial dimension of the
screw, and the cage member includes one or more corresponding
step-engaging portions for making an interference contact with the
step when the threads have been withdrawn from the cage and wedge
members a sufficient amount, so that further withdrawal of the
threads ceases to withdraw the threads relative to the cage member
while continuing to withdraw the threads relative to the wedge
member, thereby forcing the wedge member distally relative to the
cavity.
[0012] Preferably, the anchor bolt is limited to screw members
having one or more depressed portions for defining the step; more
preferably, the one or more depressed portions is a necked-down
portion of the screw member; and most preferably, the necked-down
portion is substantially cylindrical.
[0013] Preferably, in combination with any of the embodiments
described above, each of the one or more step engaging portions is
or includes a tang depending from the cage member.
[0014] Preferably, in combination with any of the embodiments
described above, the anchor bolt includes a keeper at the
distal-most end of the threaded member, for stopping the wedge
member from becoming completely disengaged with the threaded member
and thereby preventing the wedge member from being forced away from
the threaded member as a result of forcing the wedge member
distally relative to the cavity.
[0015] Also disclosed is a method for removing an anchor bolt from
a hole, where the anchor bolt includes a screw member, a wedge
member, and a cage member, the screw member having a threaded end
and defining a screw axis, the threaded end of the screw member
being threadably engaged into the wedge member, the cage member
defining a cavity through which the threaded end of the screw
member extends and into which at least a portion of the threadably
engaged wedge member is allowed to non-forcibly penetrate. The
anchor bolt has been inserted into the hole in a first axial
direction parallel to the screw axis, and the wedge member is
shaped in cooperation with the cavity to force the cavity to
undergo an expansion in one or more directions perpendicular to the
screw axis as a result of being drawn into the cavity by means of
turning the screw so as to advance the threads of the threaded end,
the anchor bolt being thereby wedged in the hole with the wedge
member stuck in the cavity.
[0016] For ejecting the wedge member from the cavity according to
the invention, the method provides a step of turning the screw
member in a first radial direction for withdrawing the threads from
the wedge member, thereby causing the screw member to translate
relative to the cage member in a second axial direction opposite
the first axial direction; and a step of stopping the screw member
from further axial translation relative to the cage member in the
second axial direction while allowing for continued turning of the
screw member in the first radial direction, so that further
withdrawal of the threads from the wedge member will result in
forcing the wedge member in the first axial direction relative to
the cavity.
[0017] Preferably, during the step of stopping, the method provides
a step of continuing to turn the screw in the first radial
direction and thereby continuing to withdraw the threads from the
wedge member, thereby resulting in forcing the wedge member in the
first axial direction relative to the cavity.
[0018] It is to be understood that this summary is provided as a
means of generally determining what follows in the drawings and
detailed description and is not intended to limit the scope of the
invention. Objects, features and advantages of the invention will
be readily understood upon consideration of the following detailed
description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 is an isometric view of a prior art basic wedge
anchor bolt.
[0020] FIG. 2 is an isometric view of an easily removable low cost
wedge anchor bolt according to the present invention.
[0021] FIG. 3 is an exploded isometric view of the wedge anchor
bolt of FIG. 2.
[0022] FIG. 4 is an isometric view of an alternative wedge
according to the invention.
[0023] FIG. 5 is a side sectional view showing the anchor bolt of
FIG. 2 installed loosely in a drilled hole.
[0024] FIG. 6 is a side sectional view of the anchor bolt of FIG. 2
in an anchoring configuration, after having been tightened.
[0025] FIG. 7 is a cut-away isometric view of the wedge anchor bolt
of FIG. 2, showing a step formed in a screw according to the
invention and a corresponding step-engaging portion of a cage
according to the invention, the step-engaging portion being shown
looking from the top, the step and step-engaging portion being in a
first relative position in which the step-engaging portion is
spaced apart from the step.
[0026] FIG. 8 is a cut-away isometric view of the wedge anchor bolt
of FIG. 2, showing the step and step-engaging portion of FIG. 7
with the step-engaging portion being shown looking from the
side.
[0027] FIG. 9 is a cut-away isometric view of the wedge anchor bolt
of FIG. 2, showing the step and step-engaging portion as depicted
in FIG. 7 in a second relative position in which the step-engaging
portion has made contact with the step, after starting from the
first relative position of FIG. 7 and withdrawing the threads of
the screw.
[0028] FIG. 10 is a cut-away isometric view of the wedge anchor
bolt of FIG. 2, showing the step and step-engaging portion as
depicted in FIG. 8 in the second relative position shown in FIG.
9.
[0029] FIG. 11 is a cut-away side elevation of a screw and cage
assembly for reference in defining an "abrupt" transition for a
step according to the invention.
[0030] FIG. 12 is a cut-away side elevation of a screw and cage
assembly showing an alternative configuration, compared to that
shown in FIGS. 3 and 7-10, for a "necked-down" portion of a screw
for defining a step according to the invention.
[0031] FIG. 13 is a cut-away side elevation of a screw and cage
assembly illustrating a "necked-up" portion of a screw for defining
a step according to the invention, for comparison with the
"necked-down" portions of FIGS. 3, 7-10, and 12.
[0032] FIG. 14 is a cut-away side elevation of a screw and cage
assembly showing an alternative configuration, compared to that
shown in FIG. 13, for a "necked-up" portion of a screw for defining
a step according to the invention.
[0033] FIG. 15 is a front elevation, taken along the line 15-15, of
the screw and cage assembly of FIG. 14.
[0034] FIG. 16 is a cut-away side elevation of a screw and cage
assembly showing a first alternative step-engaging portion to that
shown in FIGS. 12-14, according to the invention.
[0035] FIG. 17 is a cut-away side elevation of a screw and cage
assembly showing a second alternative step-engaging portion, which
is an alternative to the step-engaging portion of FIG. 16,
according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0036] FIGS. 2 and 3 show a preferred removable low cost wedge
anchor bolt 10 according to the present invention. It will be
understood that the bolt 10 may be used in any application in which
standard prior art wedge anchor bolts are used. However, the bolt
10 is particularly advantageous in applications where it is
important to be able to easily remove the bolt when its service
life is over.
[0037] At least two such applications are (1) to provide fall
protection for construction workers such as previously described;
and (2) to provide temporary anchor points for rock climbers. Like
in the construction application, low cost wedge anchor bolts used
for rock climbing are installed in holes drilled into the rock.
Once in place, the bolts are exposed to the elements making it even
more important to remove them after a time, both to ensure climber
safety and to return the rock, as much as possible, to its natural
condition. This is particularly so if the rock is ferrous and is
therefore particularly susceptible to weakening as a result of
corrosion of the anchor bolt.
[0038] As is standard in the art, the bolt 10 is preferably
provided with bolt attachment hardware 12 having two through
apertures--a through aperture 12a for receiving the screw 14, and a
through aperture 12b for receiving a caribiner as explained
previously. The apertures 12a and 12b are both contiguously
surrounded by metal, thus preventing any possibility of the screw
14 and the caribiner (assuming no failure of the caribiner itself)
escaping from the respective apertures.
[0039] Structural support for the bolt 10 is provided by a screw 14
which has a head 14a at its proximal end. The head 14a shown is
hexagonally shaped, to allow for turning the screw about its
elongate axis "L" by use of a standard hex wrench. The head 14a may
have other shapes, or include features such as slots (e.g., for
receiving standard bladed or Phillips type screwdrivers) or shaped
depressions (e.g., for receiving a standard hexagonally shaped key
or Allen wrench) allowing for the same functionality, that is, for
turning the screw by use of a standard hand tool.
[0040] The screw 14 has an elongate shank 14b which extends from
the head 14a and terminates at the distal end of the screw 14. The
shank 14b has a threaded end 14b.sub.1; turning the screw 14 in one
radial direction, e.g., clockwise about the axis L, advances these
threads in a first axial direction, along the axis L, toward the
distal end of the screw, whereas turning the screw in the opposite
radial direction withdraws the threads, in a second axial direction
opposite the first axial direction, toward the proximal end of the
screw.
[0041] So far, the screw 14 as described can be any ordinary bolt.
To form a low cost wedge anchor bolt, the screw 14 is combined with
two more parts, namely a wedge 16 and a cage 18.
[0042] The external threads of the threaded end 14b.sub.1 of the
shank 14b of the screw 14 are for engaging complementary internal
threads of the wedge 16. The wedge 16 functions in cooperation with
a cavity 18a of the cage 18 to force the cavity to undergo a radial
expansion, i.e., in directions perpendicular to the axis L, as a
result of being drawn into the cavity by means of advancing the
threads of the threaded shank. The cavity and, especially, the
wedge could have many different shapes to perform this function.
Typically, the cavity is (internally) cylindrical and the wedge is
(externally) frustoconical, as in the preferred embodiment shown in
FIGS. 2 and 3. Thus the description so far describes both the bolt
10 and the prior art bolt 2 shown in FIG. 1. And generally, there
is no intention to limit the invention to particular shapes or
configurations.
[0043] However, with reference to FIG. 4, an alternative wedge 17
having a series of spaced-apart gripping elements, here axially
extending depressions or, in a related alternative (not shown),
protusions, provides for an improved grip on the internal surface
of the cavity, and thus can be advantageous to reduce the tendency
of the wedge to spin inside the cavity as the threads are being
advanced. Such gripping elements--depressions or protusions--could
be provided in any number of shapes, patterns and configurations,
and could be provided on the interior surface of the cavity as
well, alone or in combination with gripping elements on the wedge
itself.
[0044] The cavity is provided at the distal end of the cage 18. It
can be adapted for forced radial expansion in any number of ways
known in the art. Generally, two or more lines of weakening 18b are
provided. The lines of weakening typically run axially, i.e.
parallel to the axis L, and are typically apertures that pass
through the sides of the cage. However, it is not essential for the
lines of weakening to run axially; for example, they could be
spirals. It is, however, preferable for lines of weakening to run
more axially than radially (perpendicular to the axis L). It is
also not essential for a line of weakening to be formed of holes
passing through the sides of the cage; for example, it could be a
line along which the material of which the cage is formed is
thinner, or weaker. Further, it is not essential for a line of
weakening to be continuous; for example, it could be a line of
perforations. Further still, it is not essential to provide
weakening along lines; for example, perforations or apertures could
be provided in any desired pattern, so long as sufficient physical
integrity of the cavity remains to provide for the anchoring
function. Unless otherwise indicated, there is no intention to
limit the invention in regards to the configuration of the cavity
and wedge combination for achieving the function of forced radial
expansion of the cavity by the wedge as a result of drawing the
wedge farther into the cavity.
[0045] The resulting anchoring is illustrated by FIGS. 5 and 6.
FIG. 5 shows the bolt 10 just after insertion into a hole 20 which
has been drilled into a concrete or rock wall 23. The bolt is, at
this point, loose in the hole.
[0046] FIG. 6 shows the same bolt after it has been fully
tightened, by turning the head 14a of the screw in the direction
required to advance the threads of the threaded end of the screw
into the threads of the wedge. When fully tightened, the cavity is
forcibly radially expanded, so that outer surface(s) of the cavity
is (are) pressed hard against the internal surface(s) of the hole,
and the bolt is gripped by the wall 23 as a result of friction
between the outer surface of the cage 16 and the inner surface of
the hole.
[0047] The cavity 18a resists being forcibly expanded due to its
own structural integrity, and once it has been expanded
sufficiently to seat against the interior surface of the hole, it
resists being expanded further by the interior surface of the hole.
Thus, tightening the bolt ultimately results in jamming the wedge
16 in the cavity 18a, with the wedge becoming stuck in the
cavity.
[0048] Loosening the bolt requires turning the head 14a of the
screw in the opposite direction that was required for tightening
the bolt, thereby withdrawing the threads. Because the wedge is
jammed in the cavity, the threads withdraw from the wedge, and the
screw 14 starts to back out of the cage 16. If not for the feature
described immediately below, the screw would continue to back out
of the cage until it becomes fully separated from the bolt, leaving
the cage and wedge behind, stuck in the hole as in the prior
art.
[0049] To solve this problem in accord with the invention, the
screw 14 includes a "necked-down" portion 14c, which can be seen in
FIG. 3, which results in a step 14c.sub.1 of abruptly increasing
width of the screw; and cooperating with this, the cage 16 includes
a corresponding one or more step-engaging portions 18c for
interferingly engaging with the step 14c.sub.1, once the screw 14
has backed out of the cage 16 a sufficient amount for the step to
come into interfering contact with a free end 18c.sub.1 of a
step-engaging portion.
[0050] FIGS. 7 and 8 show these features prior to the screw 14
being backed out of the cage 16 sufficiently to bring the step into
contact with the step-engaging portions of the cage; and
corresponding FIGS. 9 and 10 show the same features after such
contact has been made, at which point further relative axial
movement of the screw relative to the cage is halted. That is, the
threads will cease to significantly advance (or withdraw) relative
to the cage.
[0051] Advantageously, as the threads are still threadably engaged
with the wedge 16, continuing to turn the screw 14 so as to
continue to withdraw the threads now forces the wedge in the
opposite direction, toward the distal end of the screw, thereby
forcibly ejecting it from the cavity 18a.
[0052] Ejecting the wedge 16 from the cavity results in a
relaxation of the grip provided by the cage on the interior surface
of the hole, allowing the screw 14 to be pulled from the hole,
carrying the cage 18 along with it as a result of the interfering
relationship between the step of the screw and the step-engaging
portion(s) of the cage.
[0053] As the name implies, the step defines a region over which
there is a transition, more particularly an increase, in the radial
dimension of the screw. With reference to FIG. 11, this transition
is preferably "abrupt," meaning that, over a region of "X" units of
measure along the axis "L," measured where the screw is adapted to
make contact with the step-engaging portion, the radial dimension
"R" increases at least 2.times., more preferably at least 5.times.,
and most preferably at least 10.times.. The reason for preferring a
more abrupt transition is to confer the greatest mechanical
advantage on the step-engaging portion(s). A perfect step is where
"X" is zero, and X could also be negative (measured from the point
"P" in the direction opposite the "+" direction).
[0054] To ensure that the wedge 16 is not ejected so far from the
cavity as to become disengaged with the threads of the screw 14,
and therefore to reduce the risk that the wedge will be left behind
in the hole, a keeper 22, such as a common circlip, is preferably
attached to the screw 14 at its distal end in a standard manner.
Providing a keeper is preferable but not essential. If the threaded
end of the bolt is not too short, the wedge will remain threaded to
the screw after it has been ejected from the cavity.
[0055] To maintain low cost, the one or more step-engaging features
18c are preferably integrally formed parts of the cage 18. As best
seen in FIG. 3, this is by creating, such as by die cutting, one or
more elongate apertures 19 through the cage so as to define one or
more elongate edges of the feature 18c, which as a result become
separated from the remaining portions of the cage 18. The
aperture(s) 19 extend only partially around the feature 18e, so
that the feature 18c remains connected to the cage 18, such as in
the vicinity indicated as 21, as a cantilevered projection. This
projection, because it is cantilevered, may be bent, independently
of the surrounding material of which the cage is formed, radially
inwardly (toward the axis L), allowing the free end of the tang
(18c.sub.1) to interfere with the step (14c.sub.1).
[0056] The word "tang" is the closest English word of which
Applicant is aware that describes a step-engaging feature like that
described immediately above. According to the standard definition,
a "tang" is limited to projecting parts that are "slender." With
reference to the dimensions "a" and "b" in FIG. 3 for the
step-engaging feature 18c, and with reference to the dimension "t"
in FIG. 8 of the same feature, there may be an ambiguity as to what
is meant by "slender." As shown, dimensions "a" and "b" are roughly
equivalent, and it is to be understood that either dimension could
be significantly larger than the other. So the feature 18c is
"slender" with respect to the dimension "t," being considerably
less than either dimensions "a" or "b."
[0057] There may also be an ambiguity as to whether a "tang" as
ordinarily defined is limited to projections that are
monolithic--in the sense of being connected without joints or
seams--extensions of the structures from which they depend.
[0058] To resolve these ambiguities, as used herein the term "tang"
is defined in its ordinary manner, with the proviso that it is
connected to the structure from which it projects without joints or
seams, implying that it is formed out of the same block of material
of which the cage is formed, and it is slender, meaning for
purposes herein that, with reference to its width, length, and
depth dimensions as measured along three respective mutually
orthogonal axes, at least one of these dimensions is significantly
smaller than at least one other of these dimensions, where
"significantly smaller" means at least 3 times smaller, more
preferably at least 5 times smaller, and most preferably at least
10 times smaller.
[0059] The reason for preferring a tang that is more slender can be
appreciated by recognizing that, since the tang is formed from the
same block of material from which the cage is formed, any material
devoted to the tang necessarily subtracts from the material that
could have been devoted to the cage. Thus the reason to prefer a
tang that is more slender is to minimize the amount of material
that is not available for strengthening the cage, to use for the
step-engaging function, which requires a significant degree of
projection (e.g., a significant dimension "b" as shown in FIG. 3,
or a significant dimension "1" as shown in FIG. 14) but not much
strength.
[0060] FIG. 12 shows an alternative screw 24 and cage 28,
illustrating why it is not important for the necked down portion
24c of the screw to be cylindrical.
[0061] FIG. 13 shows an alternative screw 34 and cage 38,
illustrating an alternative to use of a necked down portion to
provide the step. In this case, there is a protruding or "necked
up" portion, or projection, 34c of the screw providing a step
34c.sub.1. The portion 34c could be a removable part, such as a
circlip, in which case the screw 34 would have a circumferential
groove for receiving the circlip.
[0062] FIGS. 14 and 15 show another alternative screw 44,
illustrating a modification of the screw 34 of FIG. 12. In this
embodiment, the screw has a projection 44c that does not encircle
the screw as does the projection 34c of the screw 34. Instead, with
reference to FIG. 14, the projection 44c extends over an arc length
"S.sub.1" and step-engaging portions 48e are arranged so that there
are no gaps of arc larger than "S.sub.2," where
S.sub.2<S.sub.1.
[0063] The embodiment of FIG. 14 is less preferred than those of
FIGS. 12 and 13 because it results in a relative abundance of
excess space between the cage and screw, allowing for an excess of
undesirable lateral movement of the screw inside the cage.
[0064] The embodiment of FIG. 15 is less preferred than that of
FIG. 14 because it requires more of the cage to be devoted to the
step-engaging function, which tends to weaken the cage if the
step-engaging portions are tangs, and which, if the step-engaging
portions are attached to the cage with joints or seams, requires
more costly manufacturing.
[0065] In FIGS. 12-15, the step-engaging portions (28e, 38c, 48c)
are tangs.
[0066] An alternative to the tang is shown in FIG. 16. The screw
could be either 14 or 24, or it could have a different
configuration from either of these. In this example the
step-engaging portion 58c is formed by adding metal to the cage. It
is not a tang because it connected to the cage with a joint or
seam.
[0067] Another possible alternative to the tang is shown in FIG.
17. Again, the screw could be either 14 or 24 or it could have a
different configuration from either of these. In this example, the
step-engaging portion 68c is formed by displacing metal of the cage
68. It is not a tang if it is not slender, and as drawn, it would
not be slender unless its measured dimension perpendicular to the
plane of the Figure is significantly less than its dimensions "l"
and "w" in the plane of the Figure.
[0068] As is standard commercial practice in the art of low cost
wedge anchor bolts, the screw, cage, and wedge are all preferably
formed of carbon steel. However, other metals--indeed other
materials (e.g., fiber reinforced plastics)-could be used without
departing from the principles of the invention.
[0069] Returning to FIG. 3, preferably the anchor bolt 10 includes
a "compression bushing" 25, which is typically formed of a polymer.
The compression bushing 25 has a relatively high compliance as
compared to the attachment hardware and the cage 18 and has a
substantial thickness allowing for a substantial amount of
deformation, qualities which allow it to prevent the attachment
hardware 12 from making hard contact with the end 18d of the cage
18 before seating against the surface 23a of the structure (see
FIG. 6). This function could alternatively be performed by a
split-ring washer, or any other structure providing the same or
similar qualities.
[0070] A split-ring washer 26 may also be provided between the
screw-head 14a and the attachment hardware to provide a positive
indication to the user of when the anchor bolt 10 is fully
tightened.
[0071] It is to be understood that, while a specific easily
removable low cost wedge anchor bolt has been shown and described
as preferred, other configurations could be utilized, in addition
to those already mentioned, without departing from the principles
of the invention. It should also be understood that, as indicated
previously, the concrete anchor point may be used in any
application that an anchor point may be used.
[0072] The terms and expressions which have been employed in the
foregoing specification are used therein as terms of description
and not of limitation, and there is no intention in the use of such
terms and expressions to exclude equivalents of the features shown
and described or portions thereof, it being recognized that the
scope of the invention is defined and limited only by the claims
which follow.
* * * * *