Note: Descriptions are shown in the official language in which they were submitted.
35~8
The present invention is directed to an anchor
assembly consisting of a dowel body and an anchor member
which can be displaced relative to the dowel body into
an anchoring position. More particularly, the invention
concerns a dowel body arranged to receive axially extending
forces at its rear end and having a supporting surface for
the anchor member adjacent its front end. The supporting
surface is inclined relative to the longitudinal axis of
the dowel body and diverges away from the axis toward the
front end of the dowel. The anchor member is a small
trapezoidal plate with a pair of sides extending trans-
versely of the axis and the longer side is located more
remGtely from the front end of the dowel. The opposite
ends of the longer side project outwardly from the circum-
ferential surface of the dowel when the assembly is
initially inserted into a borehole, that is, before the
anchoring action takes place.
When dowels are used in large quantities, for
example, for suspended ceilings and the like, it is
important to produce such dowels economically and to
ensure that they do not exceed a certain price level.
For safety reasons in the event of a fire, plastic
dowels cannot be used, instead only metal dowcls can
be employed. ~urthermore, the dowels must have a
sufficient anchoring characteristic and must bc able
to withstand dynamic alterna-ting loads.
One known anchor dowel of this general type
consists of a dowel body threaded at its rear end for
the application of force and having a recess adjacent
to and tapering toward the front end. An anchor member
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is positioned in the recess and the front end is the end
first inserted into a receiving material. In this known
dowel, the anchor member is wedge-shaped and has a detent
projecting beyond the circumferential surface of the
dowel body. A spring washer holds the anchor member on
the dowel body before the dowel is inserted into a
receiving bore.
In view of its relatively complicated shape,
the anchor member involves a complicated production
operation making its use economically questionable.
The separate holding member for the anchor member also
;; contributes to this problem. ~ncther problem is that
the detent of the anchor member which projects beyond
the surface of the dowel body, often effects only an
insufficient contact with the surface of the receiving
bore so that not only is the prespreading operation
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insufficient but the final anchoring is of questionable
effectiveness. It is not possible to enlarge the detent
beyond a certain siæe, since its enlarged size would
make it signi~icantly more difficult to drive the dowel
into a receiving bore.
In another known anchor tlowel of thc samc
general type, for reasons oE cconomy thc anchor member
is formed as a small trapezoidal plate. In place of a
separate holding member for the anchor member, the
anchor member has been held in the dowel body by magnetic
force. Such a holding action has proved to be disadvan-
tageous, since the slightest amount of dirt in the vicinity
of the anchor member reduces the holding force to the extent
that the anchor member may fall out of the dowel body before
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` it is inserted into a receiving bore. In addition, the
magnetization of the various parts involved is cumbersome
and, as a result, uneconomical.
Therefore, a primary object of the present
invention is to provide an anchor dowel assembly which
. assures not only effective use without any problems,
but also economical production and sufficient anchoring
values.
In accordance with the present invention, the
anchor dowel assembly includes an anchor member held in
a self-locking manner within a slot in the dowel body,
the slot being inclined to the longitudinal axis of the
dowel and being open toward and adjacent the front end
of the dowel body. The supportiny surface in the slot
along which the anchor member slides during the anchoring
operation is located closer to the axis of the dowel
adjacent the front end of the dowel. When the dowel
assembly is inserted into a borehole, the diameter of
the borehol~ is adjusted to -the climension of the dowel
~0 body so that the anchor member colltacts the surfaces of
the borehole. The contactiny action i'3 especially
efective in the trailing port:ion oE the anchor member
which project5 laterally from thc circumferential surface
of the dowel body. In view oE the small sizcd trapezoidal
shapéd plate employed as the anchor member, the anchor
member tapers inwardly in the direction toward the front
end of the dowel body so that the projecting rearward
portions have a saw-tooth shape. Due to the saw-tooth
shape, the dowel assembly can be inserted into a borehole
without encountering any significant resistance. However,
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the projecting portion of the anchor member ensures that
it will afford a holding action as the dowel is inserted.
When an axial force is applied to the dowel pulling it
j out of the borehole, the projecting portions of the anchor
member become tightly engaged into the wall surface of the
borehole. As a result, the anchor member remains in a
fixed position relative to the surface of the borehole,
since the slot is open toward the front end of the dowel
and the dowel can move relative to the anchor member.
When such relative movement occurs, the projecting portions
of the anchor member in contact with the surface of the
borehole increase because of the inclination of the slot
with respect to the axis of the dowel. As the withdrawing
force is increased, the anchor member becomes more tightly
secured into the surface of the borehole and provides a
fixed stop for the dowel body. Moreover, the inclined slot
in the dowel body has the effect that by increasing the
application of force in withdrawing the dowel Erom the
borehole, the anchoring action within the borehole is
similarly increased and an cffective Eorm-lockincJ connection
between the two parts oE the asembly is ensurecl.
In accordance with the inverltion, thc inc~ined
slot has the advantage tha-t it can be cconomically formed,
for example, in a sawing or cutting operation, without
involving any time consuming operations or the n~ed Eor
cumbersome tools. The width of the slot between its
opposing surfaces is preferably somewhat less than the
thickness of the anchor plate so that an effective self-
locking action is attained and an additional holding action
becomes unnecessary. Since the slot is open laterally
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from its rear end toward tne front end of the dowel, the
anchor member can move relative to the dowel for providing
an optimum anchoring characteristic.
In expansion dowels of this type it is often
difficult to effect the anchoring action, since there are
no surfaces on the dowel against which hammer blows can
be directed, accordingly, another feature of the present
invention is the provision of a suitable anchoring tool.
The tool includes a guide bar having stops at its
opposite ends with a solid annular body reciprocally
movable along the bar between its stops. Further, at
least one of the stops can be attached to the rear end
of the dowel body for applying axial force in moving
the dowel body relative to the anchor member.
After the spreading tool is connected to the
rear end of the dowel, the solid body is displaced along
the bar against the stop more remote from the end of the
dowel. The impacting action of thc reciprocating body
against the stop is transmitted to the dowel in the form
of an axially directed pulling -Eorcc. The extent to
which the anchoring of the dowel a~sembly is attained
can be controlled by varying the numer of blows providcd
by the solid body.
In a majority of such dowels the rearward erld
of the dowel is threaded so that thc anchoring tool can
be connected to it by a corresponding thread. sy providing
threads of different diameters in each of the s-tops on
the opposite ends of the anchor member, the same tool can
be utilized in dowels of different sizes. Depending on
the dowels to he anchored, the threads formed in the stops
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can be either male or female. Changeover from one type or
size of thread to another can be effected in a simple manner
by appropriately designed adapters.
The various features of novelty which characterize
the invention are pointed out with particularity in the
claims annexed to and forming a part of this disclosure.
For a better understanding of the invention, its operating
advantages and specific objects attained by its use,
reference should be had to the accompanying drawings and
descriptive matter in which there are illustrated and
described preferred embodiments o the invention.
IN THE DRAWINGS
Figure 1 is a side view of an anchor dowel
assembly embodying the present invention;
Figure 2 is another side view o the dowel
assembly of Figure 1 taken in the direction of the arrow
II shown in Figure 1, and,
Figure 3 is a side view, partly in section, of
a setting o~ tool embodying another feature of the present
invention.
In ~igures 1 and 2 an anchor dowel a~;sembly,
embodying the present invention, consists of an ~xially
elongated dowel body 1 and an anchor mcmber in the form
of a small plate. As vlewed in thc drawing, the upper
end of the dowel body 1. is its front end, that 1~, the
end first inserted into a borehole and the lower end is
its rear end. The rear end of the dowel body 1 has an
axially extending thread 3 so that axially directed forces
can be transmitted to the dowel. Adjacent its front end,
the dowel body 1 has a slot 4 open toward the front end
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of the dowel and the slot is inclined relative to the
longitudinal axis of the dowel. As can be seen in
Figure 1, the slot 4 diverges away from the dowel axis
as it approaches the front end of the element. Anchor
member 2 in the form of a small trapezoidally shaped
plate is held in engagement within the slot 4, that is,
the spacing between the opposite sur~aces of the slot
is slightly less than the thickness of the plate so
that the plate is securely held in -the slot. The trape-
zoidally shaped plate has a pair of sides extending
transversely of the dowel axis with the longer side 2a
abutting against the closed end of the slot. The opposite
ends 2b oE the longer side 2a project outwardly beyond
the circumferential periphery of the dowel. As can be
seen in Figure 2, the dimension of the plate along its
longer side 2a is greater than the diameter of the dowel
body 1. Accordingly, when the dowel assembly is inserted
into a borehole, and hefore any anchoring action takes
place, the ends 2b of the Longer side 2a extend outwardly
Erom the dowel body so that they encJacJe the surface of
the borehole. Sincc the sides 2c extending from the
opposite ends 2b of the lorlc3er side tal)er inwardly toward
one another, thc ends 2b provide a saw-tooth shape to the
rearward end of the plate. Whcn the cdowel is anchored by
effecting a relative movement between -the dowel body 1
and the anchor member 2, the plate 2 slides along the
supporting surface la within the slot and its lateral
,~ edges 2c extending between the transversely extending
;
edges progressively extencl outwardly from the circum-
ferential surface of the dowel providing a progressively
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tighter wedging action by contact with the surface of the
borehole by means of which the dowel is anchored in the
borehole.
: In Figure 3 a tool is shown for effecting the
relative movement between the dowel body 1 and the anchor
member 2. The tool consists of an annular solid body 5
reciprocally movable along an axially extending guide bar
6 between stops 7, 8 each located at an opposite end of
the guide bar. Each of the stops 7, 8 has a connection
means, such as threads 9, 10. These threads 9, 10 are
arranged to engage one end of the dowel for transmitting
axially extending forces to the dowel. In each of the
` stops 7, 8 a different size and type of thread 9, 10 is
provided so that a single tool can be used for different
dowel assemblies.
After the setting tool is attached to the dowel
body 1 by threading one of the stops 7, 8 onto the thread
3 on the rear end of the dowel body, the solid annular
body 5 is driven against the stop spaced from the rear end
of the dowel so that an axially directed pulling action is
applied to the dowel and a movement relative to the anchor
member is developed for effecting the anchoring action.
The saw-tooth shape of the ends 2b of the longer edge 2a,
while permitting the movement of the dowel body 1 and
plate 2 into a borehole, causes the plate to be gripped
in the borehole surface with the result tha-t the pulling
. action withdraws the dowel relative to the plate. The
extent of the anchoring action can be controlled by the
` number and intensity of the blows effected by the solid
¦ 30 body 5 striking against the stop spaced outwardly on the
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setting tool from the rear end of the dowel. As mentioned
previously, because of the inclined supporting surface la,
as the dowel 1 is withdrawn from a borehole, the plate 2
riding on the supporting surface 1 is displaeed laterally
so that an increasing length of plate 2 and the lateral
edges 2c begin to engage the surface of the borehole
increasing the anchoring effect.
After the application of a suitable number of
blows by the member 5, the stop 7 or 8 can be disconnected
from threads 3 of the dowel, and some other fixture may
then be attached by means of a threaded nut (not shown)
usually, as such a nut is tightened up, it will increase
the anehoring effeet of member 2 by applying further pull
out forees to the dowel, although such i-urther forees are
not in fact essential to obtain effective anehoring in
most eases.
~laving deserihed what is believed to be the
best mode by wh.ich the :invention may be performed, it
will be seen that the invention may be part:icularly
defined as follows:
Anehor assembly eompxising an axia.lly elorlcJ-Ited
dowel and an anehor member movable yenerally loncJitu(iinally
, relative to said dowel from a startincJ position i.nto an
anehored position, said dowel havincJ a Eirst cnd to be
inserted f.irst into a borehole and an opposite second enci,
means on the seeond end of said dowel ior applying axially
aetir.g forees to said dowel, a supporting surface for suppor-ting
said anehor member and located in and adjacent the first end
:; of said dowel, said supporting surface being inclined to the:
~; 30 axis of said dowel and diverging from the axis in the direction
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toward the first end of said dowel, said supporting surface
having a rear end extending transversely of the axis of
said dowel and a front end spaced in the axial direction
of said dowel from the rear end toward the first end of
said dowel and the front end of said supporting surface
being located adjacent to the peripheral surface of said
dowel, said anchor member comprising a trapezoidally shaped
plate having a pair of first sides extending transversely
of the axis of said dowel and a pair of second sides
extending between said first sides, said first sides
consisting of a longer side and a shorter side and in
the starting position of said anchor member on said
supporting surface said longer side is located adjacent
said rear end of said supporting surface and the opposite
ends of said longer side project outwardly from the circum-
ferential periphery of said dowel, wherein the improvement
comprises that said dowel has a slot formed therein with
said slot having a pair of oppositely spaced surfaces
holding said plate therebetween, one of said surfaces
being said supporting ~urface so that said 510t iS inclined
in the same manner as ~aid support.ing surface, said slot
extending generally longitudinally relative to said dowel
and at the end oE said slot closer to the second end of
~aid dowel said supporting surface is located closcr to
the axis of said dowel than the opposite surface oE said
s~.ot.
While specific embodiments of the invention have
been shown and described in detail to illustrate the applica-
tion of the inventive principles, it will be understood that
the invention may be embodied otherwise without departing
from such principles.
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