Note: Descriptions are shown in the official language in which they were submitted.
21~1750
Expansion Bolt
The invention concerns a fixture for connecting construction
elements in particular for flat furniture components, with a
tensioning member supported by a first construction element
as well as a clamping element which is attachable in an
opening of the second construction element, whereby the
clamping element exhibits a clamping bolt which can be
tightened by means of the tensioning member in an axial
tensioning direction and which, in a region of the second
construction element assigned thereto, expands transversely
to the tensioning direction, and also exhibiting a retaining
element which at least partially surrounds the perimeter of
the clamping bolt in the vicinity of the expanded portion
and is expandable transverse to the tensioning direction by
means of the clamping bolt.
In order to fashion a secure and stable connection between
the appropriate construction elements by means of fixtures
of this type, it is necessary to guarantee a secure
anchoring of the clamping bolt. Furthermore, the anchoring
of the clamping bolt must be effected directly in connection
with the initiation of the tensile load on the clamping bolt
in the tensioning direction. Under these conditions it is
clear that the construction elements which are to be
connected to each other, in the connected state, seat in
close proximity to each other so that, consequently, no gap
remains between the construction components.
As is known in the art, clamping bolts are utilized for this
purpose which are provided with a tapping screw along their
shanks. During assembly, the threaded portion of the
conventional clamping bolt is screwed into the opening in
the appropriate construction element. The thread thereby
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21~1750
cuts into the inner wall of the bore hole to secure the
clamping bolt in the axial direction.
With the thoroughly functional fixture known in the art it
is necessary to maintain relatively close tolerances on the
diameter of the bore hole in which the clamping bolt
engages. Should, namely, the diameter of the bore hole exceed
the desired diameter by too great an extent, the thread,
after screwing in, is presented with a relatively weak
foundation and the connection between the clamping bolt and
the corresponding construction element has limited
loadability. A corresponding great degree of care must
therefore be exercised when fashioning the assembly bore
hole in the construction element. In order to facilitate an
optimum interconnection between the clamping bolt and the
appropriate tensioning member, it is necessary for the
clamping bolt to be precisely directed when being screwed-
in. This, however, assumes that the clamping bolt, prior to
being screwed-in, is precisely adjusted with its threaded
portion on the edge of the bore hole. Furthermore, when
manufacturing the clamping bolt, it is necessary to cut a
thread into the region adapted for the bore hole.
In the case of another conventional fixture, a tensioning
bolt is utilized which is arranged in a displaceable fashion
within a bore passage of an expansion anchor and which
conically widens towards one end. For assembly, the
expansion bolt is inserted with its conical end together
with the expansion anchor into the appropriate bore hole of
the furniture component. By exerting a tensile load on the
tensioning bolt in the tensioning direction, the tensioning
bolt is displaced relative to the expansion anchor to
thereby expand the latter transversely to the tensioning
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direction. An anchoring of the expansion anchor in the
corresponding bore hole thereby requires a relative
displacement of the tensioning bolt in the tensioning
direction. The expansion anchor is moved along with the
tensioning bolt in the tensioning direction until the
desired clamping between the expansion anchor and the inner
wall of the bore hole is established. In this fashion, the
expansion anchor partially extends out of the bore hole. Due
to this resulting protrusion of the expansion anchor beyond
the mounting surface of the corresponding furniture
component, the furniture components which are to connected
to each other can no longer be brought into mutual contact
in the assembled state. Rather, a gap remains between the
furniture components whose gap width corresponds to the
extend of protrusion of the expansion anchor.
It is therefore the underlying purpose of the invention to
create a fixture which is characterized by simple production
and assembly and which simultaneously allows for the secure,
permanent, and directly adjacent connection of construction
elements.
This purpose is achieved in accordance with the invention
with a fixture of the above mentioned kind in that the
retaining element exhibits, on its the outer perimeter
facing away from the clamping bolt, at least one,
preferentially two support arms which protrude beyond the
outer contours of the retaining element transverse to the
tensioning direction and are elastically pivotable against
the tensioning direction. Should the diameter of the bore
hole on whose walls the clamping bolt is to be secured be
less than the required optimal diameter and if the retaining
element is resiliently configured transverse to the
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tensioning direction, it is possible, despite the diameter
deviation, to insert the clamping element, comprising the
clamping bolt and the retaining element, into the bore hole.
The force which is necessary therefor can be exercised by
hand or, if necessary, with the help of assisting means such
as, for example, a hammer. The clamping element, in the
inserted position, is clampingly held in the region of the
retaining element within the bore hole. Through activation
of the tensioning member which, for example, can be a
conventional tensioning cylinder having an eccentric guiding
curve for a bolt-head of a clamping bolt, the clamping bolt
is engaged and tightened in the tensioning direction. Due to
the initial tension on the retaining element in the bore
hole, the tightening of the clamping bolt does not lead to a
relative motion between the retaining element and the inner
wall of the bore hole. The retaining element thereby
maintains its inserted position in the bore hole and the
tensioning force acting on the clamping bolt does not cause
it to move out of the bore hole. Due to the fact that the
clamping bolt widens in the region of the retaining element
transverse to the tensioning direction and due to the
deformability of the retaining element in this direction,
the latter is pressed, along its outer periphery, against
the side walls of the bore hole when tightening the clamping
bolt in the tensioning direction. Consequently, a loadable
connection results between the clamping element in the
vicinity of the retaining element and the corresponding
construction element to cause an effective anchoring of the
clamping bolt. By continued operation of the tensioning
member, which is supported by the other construction
element, and through the resulting tensile loading of the
clamping bolt, it is possible to secure the two construction
elements to each other in a stable and permanent fashion. A
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corresponding permanent connection can also be established
with the fixture in accordance with the invention when the
diameter of the receiving bore hole for the retaining
element exceeds the desired dimension. If, in this event,
the tensioning member is operated and consequently the
clamping bolt subjected to a tensile load, the clamping
element, including the retaining element, tends to move in
the direction of the tensile load on the clamping bolt. A
motion of this kind acts, however, against the support arms
protruding beyond the outer contours of the retaining
element transverse to the tensioning direction. If the
tensioning member is operated and consequently a tensile
load exerted on the clamping bolt in the axial tensioning
direction, the support arms of the retaining elements at the
walls of the receiving bore hole, resist an axial motion of
the clamping bolt caused by the exercised tensile force. In
this fashion, the retaining element is temporarily held by
the support arms in the receiving bore hole until the
clamping bolt, due to the enlargement in the tensioning
direction of the region of the retaining element inside the
bore hole, has been sufficiently enlarged to exercise an
effective retaining connection between the retaining element
and the walls of the receiving bore. The support arms
thereby assume the function of a foundation which keeps the
retaining element in the receiving bore hole. Due to their
elastic pivotability against the tensioning direction, the
support arms represent only a minimal resistance for the
retaining element when inserting the clamping element into
the receiving bore. After introduction into the receiving
bore they spread away from the retaining element and seat in
a biased fashion on the walls of the receiving bore. The
fixture is easily manufactured in that clamping bolts can be
utilized with smooth peripheral surfaces so that no thread
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must be cut into the bolt perimeter.
A preferred embodiment of the invention provides for at
least one support on the retaining element for the support
arm which acts in a radial plane. The support serves to
accept those loads acting on the support arm when the
retaining element is rotated in the corresponding mounting
bore hole. A rotation of the retaining element can simplify
its introduction into the bore hole as well as its removal
from the bore hole. The support reduces the load on the
linking section by means of which the support arm is
connected to the outside of the retaining element.
Since the support arm or the support arms is/are pivotable
into a recess in the outer contour of the retaining element,
the mounting as well as the demounting of the clamping
element is simplified and damage to the retaining element in
the vicinity of the support arms is avoided. The support
arms thereby lie within the outer contours of the retaining
element when rotating the clamping element in the receiving
bore hole. On the one hand, an inhibiting of the turning of
the retaining element by projecting support arms is thereby
avoided; an interference between the support arms and
possible protrusions on the inner wall of the receiving bore
hole during rotation of the retaining element which, with
continued rotation, could be torn from the retaining element
is simultaneously prevented.
A preferred embodiment of the fixture in accordance with the
invention with which an external thread is provided for on
the outer circumference of the retaining element is
characterized in that the support arm is flush with the
outer contour of the retaining element in its pivoted-in
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21417SO
position and exhibits at least one ribbed structure on a
surface which is flush with the outer contour which runs in
continuity with the outer thread of the retaining element.
The threads which project radially outward from the outer
periphery of the retaining element simplify, on the one
hand, the screwing of the retaining element into and out of
the corresponding bore hole. Moreover the outer threads
improve the anchoring of the clamping element in the
corresponding construction element in particular if same is
made from press board. In addition to the automatically
resulting secure retaining connection with the wall of the
bore hole, the thread conformingly engages into the
composite structure of the construction element. Based on
the described configuration of the fixture in accordance
with the invention the effects mentioned can also be
achieved in the region of the support arms.
In order to connect the clamping bolt and the retaining
element, the clamping bolt and/or the retaining element
exhibit an appropriate carrier means on their mutually
facing surfaces which is largely transverse to the
tensioning direction and which engages into a corresponding
recess in the associated opposing surface. In this manner, a
connection is established between the two components of the
clamping element which is capable of receiving loads in the
axial direction of the retaining element as well as in a
plane directed perpendicularly thereto. The thereby
resulting form-fitting connection between the clamping bolt
and the retaining element prevents a relative motion between
these two elements when axially inserting the clamping
element into the receiving bore hole for the retaining
element as well as when screwing the clamping element in or
out, preferentially utilizing thread-like ribbed
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shoulders formed on the outer periphery of the retaining
element.
The-connection between the retaining element and the
clamping bolt likewise permits the retaining element to at
least partially overlap the clamping bolt, on its end facing
away from the tensioning member, transverse to the
tensioning direction. The described overlap of the retaining
element with the clamping bolt can be provided in addition
to or alternatively to the above described carrier means
connection. If one completely eliminates the carrier means
connection to facilitate the overlap of the retaining
element, the manufacture of the clamping bolt and of the
retaining element is thereby significantly simplified,
since, in this case, an effective form-fitting connection
between both components is guaranteed without having to
fashion carrier means and/or recesses on the connecting
surfaces in order to accomplish this goal. The clamping bolt
is secured in the direction towards the tensioning member on
the retaining element by means of the enlargement provided
for transverse to the tensioning direction.
A simplification of the assembly preparations occurs when
the retaining element is split in a largely axial direction
and when the portions of the retaining element are connected
to each other in a hinged fashion. In this case the clamping
bolt can be seated in one of the shell-like parts of the
retaining element and, subsequently, be introduced together
with the retaining element into the corresponding bore hole.
When retaining elements are made from plastic, a plastic
film could be, for example, utilized as a hinged connection
between the retaining element parts. Furthermore, following
demounting the clamping elements, the clamping bolt and
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retaining element can be easily separated from each other.
This allows for the possibility of using the same clamping
bolt a plurality of times while replacing used, deformed
retaining elements with new functional retaining elements.
In an advantageous embodiment of the invention, the
retaining element is split in a largely axial direction and
the separate parts of the retaining element are connected to
each other in a detachable fashion. A handy, easily
manufactured, and easily detachable connection between the
two parts of the retaining element is given when these parts
snap into each other.
In a further preferred embodiment of the fixture in
accordance with the invention, the retaining element
exhibits a guide shoulder which-at least partially surrounds
the outer periphery of the clamping bolt and which projects,
in the tensioning direction, beyond the construction element
associated with the assembled retaining element and which is
associated with the construction element located on the
tensioning member side. When operating the tensioning
member, the construction elements which are to be connected
to each other are pulled towards each other by means of the
clamping bolt. Thereby, the guide shoulder enters into the
bore hole of the construction element located on the
tensioning member side which is provided therefor. In the
assembled position the guide shoulder provides for a large
area radial support for the clamping bolt in the
construction element having the tensioning member. In this
fashion the connection between the two construction elements
is also stabilized transverse to the tensioning direction.
The invention is more closely described below with regard to
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~4~75~
schematic representations and embodiments.
Fig. 1 shows the partial cross section of a first embodiment
of a clamping element with molded plastic retaining
element;
Fig. 2 shows a cross section through the retaining element
in accordance with Fig. 1;
Fig. 3 shows a cross section of the retaining element of a
second embodiment of a clamping element;
Fig. 4 shows a clamping bolt which can be snapped into
engagement with the retaining element in accordance
with Fig. 3;
Fig. 5 shows a retaining element comprising two half-shells
which are connected to each other in a hinged fashion
and
Fig. 6 shows the inner surface of the half-shells of the
retaining element in accordance with Fig. 5.
Fig.1 shows a clamping element 1 for the detachable
connection of two flat furniture components which are not
shown. The clamping element 1 consists of a clamping bolt 2
as well as an expansion bushing 3 serving as a retaining
element.
During mounting, the expansion bushing 3 is introduced into
a corresponding bore hole of the relevant flat furniture
component. It is bordered on its outer perimeter by a radial
ring-like stop 4 which sidewardly projects beyond the bore
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hole of the flat furniture component and, by means of which,
the clamping element 1 is supported at the edge region of
the bore hole. Should the depth of the bore hole exceed its
desired dimensions, the stop ring 4 delimits the penetrating
depth of the clamping element 1.
In addition to the stop 4, elastically pivotable support
arms 5 as well as a plurality of radial rib-like shoulders 6
are provided for on the outer perimeter of the expansion
bushing 3. The rib-like shoulders 6 form a right-handed
thread.
A radially inwardly facing projection 7 is formed on the
first, as seen from the insertion direction of the clamping
element 1, rib-like shoulder 6. The expansion bushing 3
overlaps, by means of the projection 7, the end of the
clamping bolt 2 guided within its interior. The expansion
bushing 3, in the longitudinal direction of the clamping
bolt 2, is divided by means of two longitudinally running
separation slits 8. A guide shoulder 9 finally forms the
continuation of the expansion bushing 3 in the axial
direction and is manufactured, integral with same, from
plastic. In the assembled position, the guide shoulder 9 is
inserted into a bore hole of the second flat furniture
component. Support ribs 10, 11 serve for axial fixing as
well as for compensation of bore hole tolerances.
The clamping bolts 2 exhibit a cylindrical bolt shank 12,
which widens in a radial direction at its end located at the
expansion bushing side. The expansion bushing sided end of
the clamping bolt 2 exhibits a longitudinal section which is
largely trapezoidal and a largely rectangular cross section.
The opposite surfaces of the expansion bushing 3, molded
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onto the clamping bolt 2, are correspondingly configured.
The clamping bolt 2 widens into a bolt head on its upper
end, which is not shown, by means of which it can be brought
into engagement with a conventional tensioning member. The
conventional tensioning member is a tensioning cylinder
which is introduced into a cylindrical recess in the
appropriate flat furniture component and which is seated
therein in a rotatable fashion. An eccentric guiding groove
is fashioned in the tensioning cylinder for guiding the bolt
head. The cylindrical recess for the tensioning cylinder
communicates via an additional bore hole, whose diameter is
slightly larger than the diameter of the bolt head, with the
bore hole adapted to receive the guide shoulder 9.
The flat furniture components which are to be connected to
each other are initially provided with the necessary bore
holes and recesses. Towards this end, a bore hole for the
expansion bushing 3 is introduced into one of the flat
furniture components. The second flat furniture component is
provided with a bore hole for the guide shoulder 9, a
cylindrically shaped recess for the tensioning cylinder, as
well as with an additional bore hole for communication
between the recess for the tensioning cylinder and the bore
hole for the guide shoulder 9. The flat furniture components
are delivered to the assembly location prepared in this
fashion.
In order to connect the flat furniture components, the
clamping element 1, with the expansion bushing 3, is pressed
into the bore hole provided therefor or screwed in using the
thread provided on the outer periphery of the expansion
bushing 3. The support arms thereby come in contact with the
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edge of the bore hole and, with continued insertion of the
expansion bushing 3, are pivoted radially inward. As soon as
the stop ring 4 seats on the edge of the bore hole, the
required penetration depth of the expansion bushing 3 in the
bore hole is achieved.
Should the bore hole be larger than the the outer diameter
of the expansion bushing 3, the support arms 5 protrude
beyond the outer contours of the expansion bushing 3 in a
sideward direction to seat, tilted at an acute angle,
against the axial insertion direction on the wall of the
bore hole. When a tensile force exerted on the expansion
bushing 3 in a direction opposite to the insertion
direction, the support arms 5 engage the walls of the bore
hole and thereby secure the expansion bushing in the axial
direction.
If the acceptance bore hole for the expansion bushing 3 is
bored out with the intended dimension or, within a certain
tolerance, below this dimension, the expansion bushing 3 is
squeezed transversely to the insertion direction during
insertion into the bore hole. Due to its material
elasticity, the expansion bushing 3 is clampingly held in
the bore hole subsequent to insertion. The rib-shaped
shoulders 6 engage into the structure of the wall of the
bore hole and thereby improve the axial fixing of the
expansion bushing 3. The support arms 5 are, in this case,
pivoted into the outer contours of the expansion bushing 3.
The clamping element 1 which is anchored into the first flat
furniture component in the manner described, protrudes
beyond this flat furniture component in the axial direction
with the guide shoulder 9 as well as with the free end of
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2141750
the clamping bolt 2. During subsequent assembly, the free
end of the clamping bolt 2 is then inserted through the bore
hole for the guide shoulder 9 as well as through the
extension bore hole thereof into the cylinder shaped recess
for the tensioning cylinder. By means of rotation, the
tensioning cylinder is brought into engagement with the head
of the clamping bolt 2. As the angle of rotation of the
tensioning cylinder is increased, the bolt head is guided
along the guide curve of the tensioning cylinder to apply a
tensile force to the clamping bolt 2. As a result, the
clamping element 1 is pulled, with its guide shoulder 9,
into the bore hole provided therefor before the flat
furniture components which are to be connected seat against
each other. A continued rotation of the tensioning cylinder
then causes an axial relative motion of the clamping bolt 2
relative to the expansion bushing 3 axially secured in the
second flat furniture component. The radially broadened end
of the clamping bolt 2 located at the expansion bushing side
spreads, in consequence of this relative displacement, the
expansion bushing 3 outwardly to thereby increase the
clamping force between the bore hole wall and the outer
periphery of the expansion bushing 3 and to thereby improve
the axial fixing of the clamping element 1 in the associated
flat furniture component. A secure and permanent connection
between the two flat furniture components is thereby
guaranteed. The separation slits 8 of the expansion bushing
3, which are particularly visible in Fig. 2, lead to a
reduction in the tensile force needed to effect the relative
displacement of the clamping bolt 2, since they facilitate
the spreading out of the expansion bushing 3.
In order to disconnect the two flat furniture components,
the steps described above are reversed. When unscrewing the
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expansion bushing 3 from its appropriate bore hole, whereby
the expansion bushing 3, due to its right-handed thread,
must be rotated in a counter-clockwise direction, the
support arms 5 can seat on bearing edges 13 which are
provided in the outer periphery of the expansion bushing 3.
In this fashion, a tearing-off of the support arms 5 during
unscrewing of the expansion bushing 3 is prevented.
In the clamping element 1 of Figs. 1 and 2, the plastic
expansion bushing 3 is molded onto the clamping bolt 2,
whereas Figs. 3 and 4 show construction components which
snappingly engage each other.
An expansion bushing 3a, in use as a retaining element, only
partially surrounds a clamping bolt 2a about its perimeter.
In order to connect the two components, the clamping bolt 2a
is seated on the sideward holding guide 14 of the expansion
bushing 3a and is pushed into a holding receptacle 15 of the
expansion bushing 3a by pressure in a transverse direction.
The clamping bolt 2a exhibits, on a bolt shank 12a, a
radially outward directed carrier means 16 which engages
appropriately configured recesses in the inner wall of the
expansion bushing 3a, which are not shown. With the
assistance of carrier means 16 and the associated recesses
in the inner wall of the expansion bushing 3a, a functional
connection is established between the clamping bolt 2a and
the expansion bushing 3a in an axial as well in a rotational
direction of the clamping bolt 2a. In this manner, the
carrier means 16 of the clamping bolt 2a serve as a
foundation, in the rotational direction, for the expansion
bushing 3a, when screwing the corresponding clamping element
in or out; they prevent a relative displacement between the
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21~17~0
expansion bushing 3a and the clamping bolt 2a in the axial
direction when inserting the clamping element 2a. Otherwise
the clamping bolt 2a and the expansion bushing 3a correspond
to the construction elements shown in Figs. 1 and 2.
A retaining element, in the form of a longitudinally split
expansion bushing 3b, is represented in figures 5 and 6. The
longitudinal separation of the expansion bushing 3b effects
half-shells 17, 18 which are connected to each other in a
hinged fashion by means of plastic film 19. The half-shells
17, 18 exhibit recesses on their inner surface for the
acceptance of a clamping bolt. In preparation for assembly
of the clamping element, a clamping bolt is first inserted
into the recess in the half-shell 17 or 18. The half-shells
17 and 18 are subsequently folded together.
