Expansion dowel

An expansion dowel (1) is formed of an axially extending dowel member (2) having a leading end and a trailing end. The trailing end has an outwardly projecting collar (9) with an expansion region extending axially from the trailing end toward the leading end with at least one axially extending slot (7) or breakout groove therein. The dowel member (2) has a central throughbore (3) arranged to receive an expanding element (8). Throughbore (3) has an inside thread (15) in its leading end region. The expanding element (8) is an axially extending sleeve insertable into the trailing end of the throughbore (3) for expanding the expansion region (6).

BACKGROUND OF THE INVENTION 
The present invention is directed to an expansion dowel comprising an 
axially elongated cylindrically-shaped dowel member having a collar and an 
expansion region containing at least one of an axial slot or a breakout 
groove. The dowel member has an approximately central throughbore shaped 
to receive an expanding element. 
Expansion dowels of the generic type are in very wide use. They are 
utilized in rock, concrete, masonry and similar receiving materials. 
Moreover, they are also used in lower strength receiving materials, such 
as wood. The collar at the trailing end of the expansion dowel affords a 
precise setting depth independently of the borehole depth. Sheet metal 
plate is often used in forming an expansion dowel, since it is inexpensive 
and easy to form. An expansion dowel is disclosed in DE-C-841 949 
comprising a cylindrically shaped dowel member with a collar. The dowel 
member has a throughbore and is slotted along an axially extending side. 
This expansion dowel is intended to be expanded, without an additional 
expansion element, for fixing a lug or gudgeon, for instance the gudgeon 
of a door handle, in a reliable manner without using screws, bolts or 
rivets. The dowel has an expanding member at its leading end insertable 
into a cross sectional constriction in the throughbore, and the 
constriction is widened when a peg or gudgeon is driven into the 
throughbore and presses the leading end of the dowel member into the 
borehole wall. The peg for the door handle, driven into the throughbore, 
functions as an expanding element. As a result, the expansion dowel is 
self-locking, whereby driving the peg is possible, however, extracting the 
expansion dowel is prevented. While this type of anchoring an expansion 
dowel in very soft receiving material may lead to adequate retaining 
values, for instance for door handles and the like, the expansion dowel is 
not suitable for use in stronger receiving materials. In stronger 
receiving materials, such as rock, concrete and masonry, the leading edge 
is pressed only slightly or not at all into the surface of the borehole. 
Rather, the region of the cross sectional constriction is simply urged 
outwardly and is plastically deformed. It is impossible to obtain adequate 
retaining values in this manner. In receiving materials of lower strength, 
however, it is also impossible to provide anchorages for this type of 
expansion dowel which satisfy higher retaining value requirements. 
Therefore, it is desirable to provide an expansion dowel which can be 
fabricated from sheet metal plate and which is suitable for use in 
receiving materials of lower strength, and can also be used in strong, 
solid receiving materials, such as rock, concrete, masonry and the like. 
The expansion dowel should provide adequate retaining values in the broad 
range of receiving materials. Further, the expansion dowel is to be used 
for direct attachment of elements without using screws, bolts as well as 
permitting conventional attachments like screw members. No additional 
setting tools are to be needed for expanding such dowels. 
SUMMARY OF THE INVENTION 
Therefore, it is a primary object of the present invention to provide an 
expansion dowel which affords the above requirements. In accordance with 
the invention, an expansion dowel is provided having an axially extending 
cylindrically shaped dowel member with a collar and an expansion region 
containing at least one of an axially extending slot or a breakout groove. 
The dowel member has an approximately central throughbore shaped to 
receive an expanding element. An inside thread is provided in the leading 
end region of the throughbore. The expanding element is in the form of a 
sleeve and is insertable into the trailing end region of the throughbore 
and such trailing end region forms the expansion region of the dowel 
member. 
Such an expansion dowel can be used universally due to its inventive 
features. 
The expansion region equipped with a slot or breakout groove is disposed in 
the trailing end region of the dowel member. The expansion element can be 
driven in this region into the central bore and is in the form of sleeve. 
No special setting tool is needed for driving sleeve into the borehole, it 
can be driven by a hammer. In this arrangement, a flush expansion of the 
expansion dowel independent of the borehole is assured by the collar 
located at the trailing end dowel member. The expanding action is achieved 
by the pressure developed in the trailing end region of the dowel member, 
forming the expansion region in the borehole. The leading end region in 
the borehole is provided with an inside thread. Journals or lugs can be 
driven directly into the sleeve, and, for instance, door handles can be 
attached in this manner. The presence of an inside thread in the leading 
end region of the throughbore affords the possibility of a bolt or screw 
connections. The length of the screw is determined only by the dimension 
of the item to be attached and the depth of the borehole. In a preferred 
embodiment of the expansion dowel of the present invention, the expansion 
region of the dowel member extends approximately for 1/2 to 3/4 of the 
axial length of the expansion member. As a result, a sufficiently long 
expansion region is afforded which, together with a sleeve of adequate 
length as the expanding element, provides adequate retaining values in all 
types of receiving materials. 
Preferably, the axial length of the sleeve is selected so that in the 
inserted state it does not project outwardly from the trailing end of the 
throughbore. In such an arrangement, the sleeve terminates flush with the 
collar on the trailing end of the dowel member. Accordingly, elements to 
be anchored fit flush with the dowel member. 
In a preferred embodiment of the invention, the leading end region of the 
throughbore, containing the inside thread, has a smaller diameter than the 
trailing end region. In the case of a direct fastening of a peg or pin in 
the sleeve, it abuts, if it is driven forwardly into the dowel member 
together, with the peg at the end of the leading end region spaced from 
the leading end of the expansion dowel. 
Accordingly, only the peg or pin is advanced if the forward driving action 
is continued. It is advantageous if the expanded sleeve has an inside 
diameter greater than or equal to the diameter of the leading end region 
of the throughbore. In this way it is assured that the inside thread in 
the leading end region of the throughbore is accessible for inserting a 
screw. The dowel member of the present invention can be formed of plastics 
material or metal. Preferably, the dowel member an the expansion sleeves 
are fabricated from sheet metal plate which is easy to fabricate. 
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 drawing and descriptive matter in which there is 
illustrated and described a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
In FIGS. 1 and 2 an expansion dowel 1 is illustrated. The expansion dowel 1 
comprises an axially extending cylindrically-shaped dowel member 2 with an 
axially extending central throughbore 3. As viewed in the drawing, dowel 
member 2 has a leading end at the left hand end and a trailing end in the 
right hand end and is insertable into a borehole B in the setting 
direction S, note the arrow shown in FIG. 1. 
Dowel member 2 has a leading end region 4 extending from its leading end 
toward its trailing end and a trailing end region 6 extending from the 
trailing end to the rear end of the leading end region. The trailing end 
region 6 of the dowel member forms the expansion region and has at least 
one axially extending slot 7. A breakout groove can be provided in place 
of the slot 7. A collar 9 is formed on the trailing end of the dowel 
member extending radially outwardly from the outside surface of the dowel 
member and the collar serves as a stop when setting the expansion dowel 
into the borehole B in a receiving material A, such as concrete. 
The central throughbore 3 is arranged in the trailing end region 6 of the 
dowel for receiving an expanding element in the form of an axially 
extending sleeve 8. As shown in FIG. 2, the outside diameter of the sleeve 
is approximately 0.5 mm to 1.5 mm, plus or minus 0.2 mm manufacturing 
tolerance, larger than the inside diameter d of the trailing end region 6 
of the dowel member which forms the expansion region. The expansion region 
or trailing end region 6 extends for approximately 1/2 to 3/4 of the 
overall axial length 1 of the dowel member 2. When the sleeve 8 is driven 
in the setting direction S into the central throughbore 3 it widens the 
expansion region 6 which widening is effected due to the axially extending 
slot 7. The axial length of the sleeve is selected so that when it is 
driven into its final position its trailing end is located flush with the 
collar 9 of the dowel member 2. 
The leading end region for throughbore 3 has a smaller inside diameter f 
than the inside diameter d of the trailing end region 6 and has an axially 
extending inside thread 5 forming an engagement means for an attachment 
screw, not shown. The inside diameter h of the sleeve 8 is greater than or 
at the least equal to the inside diameter f of the leading end region in 
the throughbore 3. 
In the embodiment illustrated, the outside surfaces of the dowel member 2 
and the sleeve 8 taper inwardly toward the leading ends. It should be 
noted that the embodiment illustrated is only by way of example and not 
limitation. It is possible that the dowel member 2 and the sleeve 8 can 
have outside cylindrical shapes of a constant diameter for their full 
axial length. 
The expansion dowel 1 of the present invention can be fabricated from 
plastics or metal. Preferably, the dowel member 2 and the sleeve 8 are 
fabricated from sheet metal plate which is easy to form. 
The expansion dowel of the present invention can be used in all types of 
receiving materials. The expansion region 6 has a slot 7 or a breakout 
groove located in the trailing end region of the dowel member. The 
expansion element, to be driven into the central throughbore in the 
expansion region, is in the form of a sleeve. Driving the sleeve into the 
dowel member does not require a special setting tool, a hammer is all that 
is required for driving the sleeve into its position within the dowel. A 
flush expansion is assured, independent of the borehole depth, due to the 
collar 9 provided at the trailing end of the dowel member. 
The expansion is achieved within the throughbore by the pressure applied in 
the trailing end region of the dowel member which forms the expansion 
region. The dowel member has an inside thread 5 in its leading end region. 
Pegs or pins can be driven directly into the sleeve and door handles can 
be attached in this way. The inside thread 5 in the leading end region of 
the throughbore 3 affords engagement means for threaded attachments. The 
length of a screw for a threaded attachment is determined solely by the 
thickness of the element to be attached and the depth of the borehole. 
While specific embodiments of the invention have been Shown and described 
in detail to illustrate the inventive principles, it will be understood 
that the invention may be embodied otherwise without departing from such 
principles.