AU489552B2 - Expandable dowel - Google Patents

Description

85.498/75

Tho invention relates to an expandable dowel

or expandable bolt for insertion into a borehole in

the masonry or the like.

A prior proposed expandable dowel comprises an

expanding sleeve with multiple slots extending from

the one end thereof, the slotted portion being ex-

pandable by at least one conical expanding member

which engages into the slotted end of the sleeve.

A screwthreaded bolt extends through the expanding

sleeve and is in screwthreaded engagement with the

expanding member and has a shaft which is provided

with a spacer sleeve adjoining the unslotted end of

the expanding sleeve, said spacer sleeve being re-

tained on the ccrewthreaded bolt by the bolt head

or by a nut screwed upon the screwthroaded bolt with

an interposed washer. In utilising such a prior

proposed dowel, the object to be supported is clamp-

able between the underside of the bolt head or was-

her and masonry or the like in which a borehole has

been formed, the dowel being inserted in the bore-

hole.

Expandable dowels of this kind are used, for

example, for mounting items such as a metal plate on

a solid wall or the like by insertion of. the dowel in

a bore in the wall, the dowel also passing through a

bore in the specific item. The bores are sufficien-

tly large to ensure that the expandable dowel can be

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inserted through the aligned bores until the washer

or the bolt head abuts on a surface of the item

after the item is placed on the wall in the intended

mounting position. Rotation of the bolt head or of

the nut by means of a suitable tool draws the ex-

panding member into the slotted end of the expanding

sleeve so that by said sleeve expands and thus the

dowel is anchore in the bore provided in the wall at

a depth defined by the length of the spacer sleeve

and the expanding sleeve. Since the bolt head or

nut can be tightened only until it abuts on the

outer endface of the spacer sleeve whose inner end-

face engages with the expanding sleeve, it is poss-

ible that evenpowerful tightening of the bolt head

or of the nut does not permit the item to be an-

chored sufficiently firmly on the solid wall be-

cause no further movement of the bolt head or nut

is permissible after the washer or bolt head engages

with the spacer sleeve.

According to the present invention there is

provided an expandable' dowel for insertion into a

borehole comprising an expandable sleeve with one or

more slots extending from one end thereof and ex-

pandable by at least one expanding member which engages

the slotted sleeve, a screwthroadod bolt which is in

screwthreaded engagement with the expanding member

and has a shaft which is passed through a spacer

sleeve adjacent the unslotted end of the expandable

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sleeve, said spacer sleeve being retained on the

screwthreaded bolt by a bolt head or by a nut

screwed upon the screwthreaded bolt wherein the

spacer sleeve or a washer is located between

the spacer sleeve and said bolt head or nut con-

structed so that it can be elastically or plastically

defored by up to a predetermined amount under the

influence of a force which acts axially of the bolt.

In embodiments of the invention it is necessary to

provide only short deformation distances since the

items to be mounted by the dowels are generally

rigid.

In order to permit such deformation, it is

possible to arrange that the mechanical strength of

at least one end of the spacer sleeve is weakened for

example the ability to withstand axial stress is dimi-

nished by a reduction of the material thickness.

In the simplest, case, this is achieved by

reducing the wall thickness of thespacer sleeve by a short conical counter sink or chamfer. Con-

veniently the end of the spacer sleeve whose wall

thickness is reduced is additionally weakened by

slots, such as short axial slots.

As an alternative or in addition to the above is

a device where a washer is provided for the desired

deformability can be achieved by providing the

region of the washer adapted to be within a bore

provided in an item which is to be mounted with sec-

tions which are pressed out of the washer plane

and can be re-deformed into the washer plane by

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forces acting at right angles, thereto, said sections

being directed towards the spacer sleeve and engaging

with the endfaco of said spacer sleeve when the nut

or the bolt head is tightened.

One preferred embodiment of the invention is

constructed so that short slots are cut into the

washer extending from its central aperture and ma-

terial situated adjacent to the slots is pressed

out of the washer plane.

To this end, it is advisable that at least

two, but preferably three, slots are provided at a

regular angular distribution around the central ap-

erture.

In order that-the invention may be more readily

understood and so that further features thereof may

be appreciated the invention will now be described

by way of example with reference to the accompanying

drawings, in whicht-

Figure 1 is a side view of one embodiment of

an expandable dowel in accordance with the invention,

Figure 2 is a part sectional view illustrating

the system of mounting an item on a solid wall using

the expandable dowel illustrated in Figure 1,

Figure 3 is a part sectional view to an enlarged

scale of the part of the mounting system which is

marked by the dash-dot circle 3 in Figure 2,

Figure 4 shows a washer suitable for use with an

498/75

expandable dowel in accordance with the invention,

Figure 5 is a sectional view along the line

of Figure 4,

Figure 6 is a sectional view illustrating an

end part of a spacer sleeve which can be used in

an expandable dowel in accordance with the inven-

tion, and

Figure 7 is a sectional view corresponding to

Figure 6 and illustrating a modified embodiment of

the spacer Esleve.

Figure 1 shows an expandable dowel in accor-

dance with the invention and referenced in its

entirety with the numeral 10. The dowel 10 com- prises an expandable sleeve 12 provided at one

end with a plurality of axially extending slots, and

a frusto-conical expanding member 14 which engages in

to the said slotted end of the sleeve. The expanding member 14 is provided with an internally screwthreaded

bore and is in screwthreaded engagement with an

elongated screwthreaded bolt 16 which extends through

the expandable sleeve 12 and through a spacer sleeve

18 which is disposed adjacent to end in axial align-

ment with the expandable sleeve. A washer 20 is

mounted on the end of the screwthreaded bolt 16

which is remote from the expandable sleeve. A nut 22 which is screw-mounted on the screwthreaded bolt

16 in front of the washer 20 retains the individual

components of the expandable dowel 10 and also

serves to expand the dowel

85498/7s In place of the nut 22, it is possible for the

outer end of the screwthreaded bolt 16 to be pro-

vided with a bolt head which is integrally att-

ached to the screwthreaded bolt and to which a

spanner can be applied.

A series of projections 24 are stamped to

project from the underside of the washer 22 so that

the endface of the spacer sleeve 18 nearest to

the washer is spaced at a distance from the under-

side thereof, this spacing being visible in Figure

1. (see also distance x in Figures 2 and The

projections 24 are such that they can be redeformed

into the plane of the washer.

Figure 2 shows the mounting of an item,

designated with the numeral 26, on the surface area

28 of a structure 30, in the form of a concrete

wall.

The item 26 and the structure 30 are pro-

vided with bores of the same diameter in flush align-

ment, the bore diameter being selected so that the

expandable sleeve 12 in its unstressed state, as well

as the spacer sleeve, whose diameter approximately

equals the diameter of the unstressed expandable

sleeve, can be inserted from the outside of the item

24 to be mounted through the bore 32 into the

bore 34 until the washer 20 bears upon the surface

of the item 26. This kind of mounting in which the

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dowel is inserted into the bore.of the base

through the bore of the object which is to be mounted

is referred to as insertion mounting.

After the dowel is inserted in the manner

described above, the expandable sleeve 12 is ex-

panded by rotation of the nut 22 while the item

26 is simultaneously thrust against the surface

area 28, thus anchoring the expandable sleeve 12

in the bore 34. If a conventional flat washer were to be used as washer, it would not be possible

to apply additional stress to the mounted item

26 against the surface area 28 because the spacer

sleeve 18, whose inner end engages with the ex-

pandable sleeve 12, would then engage with the washer

with its outer end and further stressing of the

item 26, would not be possible.

However, in the illustrated embodiment of the

invention the underside of the washer nearest to

the spacer sleeve 18 is provided with the previously-

mentioned projections 14 which can be re-deformed

into the plane of the washer, thus providing an

additional stressing path x to provide stress for

the item 26 between the surface area 28 and the

washer 20. This ensures that the item 26 can be

mounted on the surface area 28 with an adequate thrust

force, even if the connection initially does not have

adequate strength after the expandable sleeve 12 is

expanded.

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The embodiment of the washer 20 used in con-

junction with the expandable dowel 10 illustrated

in Figure 1 is shown in Figures 4 and 5. It will be appreciated, however, that other formis of washer

could be used. The projections 24 in the washer

are formed by cutting at least two and preforab,y

three short radial slots 38 into the flat

from the central aperture 36 thereof at uniform

angular distances from each other, so that the

material of the washer adjoining one side of the

slot is pressed out of the plane of the washer.

The projections 24 thus formed can be re-deformed

into the plane of the washer 20 if the nut 22 is

sufficiently strongly tightened. The projections

24 are located so that initially, in use, they lie

within the bore formed in the item 26 to be mounted

by the dowell.

As an alternative to the washer 20 described

above or, where appropriate, in conjunction with

such a washer, it is also possible for one, or

where necessary both, end zones of the spacer

sleeve 18 to be constructed so ~as to provide a

apecific axial deformability. Spacer sleeves of

this kcind are shown in Figures 6 and 7. The do-

formability of the sleeves 18 in the end zone of

the embodiment illustrated in Figures 6 is achieved

by a reduction of the material thickness of the sle-

eve 18! in the end zone thereof and by additionally

provided slots 40. The wall thickness of the sleeve

1 0 10489552

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18 is reduced by conical countersinking or chamfering

of the sleeve bore.42.

The end region of the sleeve bore of the spacer sleeve 18 which is shown in Figure 7 is

expanded by means of an end mill so that the milled

region of the sleeve has only a relatively slight

wall thickness which is so thin in the illustrated

example that no additional slots are required for

further weakening of the wall.

The dowel construction generally as described above can be embodied not only in the dowels illus-

trated in Figure 1 which can be conically expanded

merely by means of an expanding member disposed

on the inner end of the dowel, but the deformable

washer 20 as well as the deformable spacer sleeve

18 can also be employed in conjunction with cylin-

drically expanding dowels of the kind disclosed in

the German Patent Specifications/l,230,621 and 1,

625,394. In these dowels an expanding member can be provided in the region of the outer expandable

dowel end in addition to the expanding member which

is provided on thr inner end of the expandable dowel.

It will, of course, be readily appreciated

that this invention may be applied to double-expanding

dowels. Such cylindrically or double-expanding dowels are disclosed in the above-mentioned Patent

Specifications and, the further modification of

such dowels to embody this invention requires adap-

85.498/75

tation only of those parts (spacer sleeve, washer) which

are identical to corresponding parts of the dowel des-

cribed in detail in conjunction with Figs. l.and 2, of

the accompanying drawings.

The spacer sleeve and the expandable sleeve may,

of course, be a single integral member.

It is to be understood that the invention is not

limited to the particular embodiments described above,

but is solely limited by the scope of the appended claims.

Claims (1)

1. 85498/75

   The claims defining the invention is as follows:

   1. An expandable dowel for insertion into a borehole,

   comprising: expandable sleeve means with at least one

   slot extending from one end thereof, at least one ex-

   panding member engaging said sleeve means at said one

   end for exansion thereof, spacer sleeve means adjacent

   that end of said expandable sleeve means which is opposite

   said one end and having an end face, a screw-threaded bolt

   in screw-threaded engagement with said expanding member and

   having a shaft which is passed through said spacer sleeve

   means and said expandable sleeve means, means on said screw-

   threaded bolt adjacent said spacer sleeve means for retaining

   said spacer sleeve means on said screw-threaded bolt, and

   washer means located between said spacer sleeve means and

   said means on said screw-threaded bolt, said washer means

   having a first substantially flat portion located outside

   the projection of a borehole into which the dowel is to be

   inserted and a second portion within the projection of the

   borehole, said second portion being provided with deform-

   able sections bent outwardly with respect to the plane of

   said washer m-ans and extending in a direction toward said

   spacer sleeve means, whereby upon tightening of said means

   on said screw-threaded bolt said sections first engage said

   end face of said spacer sleeve means and thereafter are de-

   formed back into the plane of said washer means.

   2. An expandable dowel according to claim 1, wherein said

   means on said screw-threaded bolt is a bolt head integrally

   connected to said bolt.

   3. An expandable dowel according to claim 1i, wherein

   said means on said screw-threaded bolt is a nut. 13 489552 1 i

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   4. An expandable dowel according to claim 1, wherein

   said sections are elastically deformable.

   An expandable dowel according to claim 1, wherein

   said sections are plastically deformable.

   6. An expandable dowel according to claim 1, wherein

   said washer means is provided with a central aperture, and

   with slots extenJing from said central aperture, said

   sections being formed by material adjacent said slots bent

   out of the plane of said washer means.

   7. An expandable dowel according to claim 6, wherein

   at least two slots are provided in equal angular distri-

   bution around said central aperture.

   8. An expandable dowel according to claim 6, wherein

   at least three slots are provided in equal angular dis-

   tribution around said central aperture.

   May, 1977.

   PHILLIPS ORMONDS FITZPATRICK

   Attorneys for:

   HEINRICK LIEBIG