Redetachable, self-adhesive hook or similar fixing device having a baseplate, characterized by a strip of a double-sided adhesive film which is such that the bond obtained with it can be separated again by pulling on it so as to stretch it, which film carries on its front face the baseplate and with its rear face is bonded to a substrate, the separation of the bonded baseplate of the fixing device together with the strip from the substrate taking place by rotation of the baseplate essentially in the plane of the bond.

DESCRIPTION 
The invention relates to a self-adhesive, redetachable hook or a similar 
fixing device which can be detached again from the substrate without any 
residue or damage. 
For a relatively long time commercial hooks have been known which are fixed 
to the substrate by means of double-sided adhesive foam strips. Subsequent 
detachment is very difficult to achieve, and usually entails the 
destruction of the hook. Furthermore, residues of the adhesive strip 
remain on the substrate. 
Self-adhesive hooks or comparable devices are known, inter alia, from 
German Patent DE 42 33 872. This patent describes a hook which is bonded 
to the substrate by means of a strip of an adhesive film, the adhesive 
film strip having a nonadhesive grip tab. To detach the hook from the 
substrate again, the adhesive film strip is drawn in the plane of the bond 
by pulling on the grip tab, and thereupon becomes unstuck. In order that 
the hook can be redetached from the substrate, it is absolutely necessary 
for the adhesive film strip to be bonded under the hook in such a way that 
the grip tab is visible. 
This permanently visible grip tab of course mars the visual appearance of 
the stuck-on hook, but also has technical disadvantages. This is because 
the grip tab is supplied without protection against external influences. 
Heightened UV radiation or solvents impair the stability of the grip tab, 
which then readily tears on detachment under the effect of pulling. 
Subsequently, separation of the hook from the substrate is again possible 
only with destruction of the substrate or of the hook. 
Hooks of this kind are already available commercially, under the name "TESA 
POWER-STRIPS MIT HAKEN".RTM.mit Haken="with hook"!. 
A comparable hook is disclosed in the PCT application WO 94/21157. The hook 
shown in this application uses an adhesive film which is highly elastic 
and, moreover, is not resilient. 
Also available commercially are the "TESA POWER-STRIPS 
SYSTEMHAKEN".RTM.system hooks!. In order to attach such a hook to the 
substrate, a baseplate is first of all stuck by means of a strip of the 
abovementioned adhesive film, it being necessary again for the grip tab to 
remain visible. 
The respective hook is then placed onto the baseplate. This hook, however, 
features a relatively complex method of bonding and, furthermore, it is 
complex to prepare as a result not least of the two-part configuration and 
is therefore expensive. 
A feature common to all of the abovementioned systems, however, is that 
they also have practical disadvantages which may restrict their use. For 
instance, the procedure of proper bonding requires an explanation for the 
user. The reason for this is that, if the user fails to stick the hook in 
such a way that the grip tab of the adhesive film is visible, subsequent 
separation of the hook from the substrate is no longer possible. Indeed, 
the detachment of the hook or of the said baseplate takes place by pulling 
on the grip tab parallel to the plane of the bond. The resulting extension 
of the adhesive film results in a reduction in the bond strength, and the 
adhesive film becomes detached without residue from the substrate and from 
the hook as well. If the adhesive film is employed incorrectly, the 
desired separation can only be achieved using appropriate force. However, 
this leads in every case to the destruction of the hook; furthermore, the 
substrate may also be damaged as well. 
Finally, as result of the particular method of bonding, conventional hooks 
cannot be used in many places because there is no possibility of pulling 
the grip tab in the direction of the plane of the bond. Utility is 
restricted further still by the fact that in some places it is not 
possible to have the grip tab freely accessible at all, for example on 
edges or projections. 
The object of the invention, therefore; was to provide a self-adhesive, 
redetachable hook or similar fastening device which does not have the 
abovementioned disadvantages. 
This object is achieved by means of a self-adhesive, redetachable hook or 
similar fixing device as is described in Patent Claim 1. Further 
embodiments are the subject of the subclaims. 
The invention relates accordingly to a redetachable, self-adhesive hook or 
similar fixing device with a baseplate and with a strip of a double-sided 
adhesive film. A feature of the adhesive film is that the bond obtained 
with it can be separated again by pulling on it so as to stretch it. 
The front face of the adhesive film carries the baseplate of the fixing 
device, preferably in such a way that the front face of the strip is 
covered completely by the baseplate; the rear face of the adhesive film is 
covered with a release laminate, for example a release film or siliconized 
release paper. Following the removal of the release laminate, the rear 
face of the strip is bonded to a substrate. 
The bonded baseplate together with the strip is separated from the 
substrate by rotating the fixing device essentially in the plane of the 
bond. 
The baseplate can have a thickness of less 5 mm. In addition, the baseplate 
can be provided with at least one groove and/or at least one bore. 
These techniques of implementing the baseplates mean that the necessary 
torque for separating the baseplate and thus the fixing device is possible 
only by means of an appropriately shaped key. This key embraces the 
baseplate similarly to the way a known socket spanner embraces a hexagonal 
nut. Alternatively, the key is shaped such that it engages by means of 
pins into the grooves or bores in the baseplate. 
In order to utilize the baseplate to the optimum the strip can be shaped 
substantially like the baseplate. This produces a high holding force on a 
relatively small area. 
The adhesive film is preferably elastically or plastically extendable with 
or without an intermediate backing, and is also preferably based on 
thermoplastic rubber and tackifying resins, being of high elasticity and 
low plasticity. 
The adhesion of the adhesive film is advantageously less than the cohesion, 
the adhesion largely disappears when the film is extended, and the ratio 
of peel force to tear load is at least 1:1.5. 
The fixing device consists preferably of plastic or metal, and so 
polyethylene terephthalate, polystyrene and ABS are particularly suitable. 
A hook according to the invention and a fixing device according to the 
invention are outstandingly suitable for avoiding the disadvantages of the 
systems known to date. Because of the rotation of the hook for separation 
from the substrate it is no longer necessary to bond the adhesive film in 
such a way that a grip tab remains visible. Furthermore, the adhesive tape 
no longer requires any grip tab at all. 
Consequently, tearing of the grip tab in the course of pulling is ruled 
out. 
In addition, the user is readily able to stick on a hook according to the 
invention in the proper manner even in difficult circumstances of use, 
since the user also knows this method of bonding from the very simple 
hooks which have been known for a long time. 
A hook according to the invention can, furthermore, be bonded--owing to the 
particular technique of detachment--even at places which were previously 
inaccessible to the conventional hooks because for lack of space the 
required pulling on the grip tab is not possible. 
To detach the bonded hook, the hook itself, which is accordingly of stable 
construction, is rotated. Alternatively, it is also possible to take the 
baseplate of the hook and move it by a sufficiently large angle. For this 
purpose the baseplate advantageously has a thickness of at least 5 mm. 
Depending on the size and type of the adhesive film strip, of the baseplate 
and of the substrate on which the hook is bonded, different hook loading 
limits can be achieved. The substrate must be level, firm and dry; further 
thorough cleaning is also advisable directly before bonding in order to 
ensure the permanent and reliable bonding of the hook. 
In one particular embodiment of the baseplate of the hook it is possible to 
avoid a further, hitherto unsolved problem. A feature of the conventional 
systems is that the hook can be removed without residue at any time, but 
thus also by anyone. Especially when such hooks are stuck in areas with a 
changing public, for example in hotel rooms, restaurants or supermarkets, 
there is the risk of the hook, which indeed is reusable, being removed 
without authorization. If the baseplate is very thin or covers only a 
small area in total, the respective user can no longer detach the 
baseplate and thus the fixing device as a whole with the hand but only 
using a tool. The use of a key as described as the tool is a possibility. 
If the baseplate is circular it can be provided with a groove which is 
engaged by the specific key having an appropriately shaped pin. It is also 
possible to provide at least one recess, for example a bore, in the 
baseplate, into which the key with the appropriate number of pins engages. 
However, the invention is not restricted to these possibilities; rather, 
other possible embodiments of a key are also within the scope of the 
invention. 
Following the separation of the hook together with the adhesive film from 
the substrate, the adhesive film itself is separated from the hook by 
simply pulling the adhesive film in the direction of the plane of the bond 
from the hook. 
The hook is thus always reusable. 
The intention of the text below is to illustrate the invention in more 
detail with reference to an example, without intending to be limiting in 
any form.

Onto this hook 1, with its rectangular baseplate 2 measuring 20 mm.times.20 
mm and carrying a pin-like extension 3 on its front face, there is first 
of all bonded a strip 4 having adhesive film of the following composition 
and size. 
The overall hook 1 consists of ABS. 
The adhesive film 4 consists of a mixture of 50 parts of SIS TRIBLOCK 
polymer having a block polystyrene content of 29% by weight (VECTOR 4211, 
Dexco), 50 parts of a penta ester of partially hydrogenated rosin 
(PENTALYN H-E, Hercules) and 1 part of a phenolic anti-aging agent. This 
composition is extruded in a layer thickness of 600 .mu.m onto 
double-sided siliconized release paper, and the laminate comprising 
adhesive composition and release paper is wound up into 50 mm wide stock 
rolls. 
The adhesive film 4 is subsequently covered on both faces with a 30 .mu.m 
thick siliconized polypropylene film. 
In the next operation, strips 4 measuring 15 mm.times.15 mm are punched out 
by means of a lift punch. 
In this context, the hook 1 is bonded with the adhesive film 4 in such a 
way that the entire strip 4 is masked by the baseplate 2. 
The hook 1, now covered with the adhesive film 4, is applied to a dry, 
level and clean tile 6 by first peeling off the release film 41 which is 
on rear face of the adhesive film 4, and then pressing the hook 1 with the 
adhesive film 4 firmly against the tile 6 for five seconds. 
In this case the hook 1 is firmly anchored and can now carry weights of up 
to half a kilogram. 
In order to detach the hook 1, the baseplate 2 is taken firmly from both 
faces and is rotated clockwise in the plane of the bond. As a result, the 
adhesive film 4 separates from the tile 6 without leaving any residues or 
causing damage. 
Separation can be effected alternatively by engaging a key having an 
appropriately shaped pin into the groove 21 in the baseplate 2 of the hook 
1 which at the same time closely embraces two faces of the baseplate 2 in 
the manner of a generally known socket spanner. This key is able to 
transfer outstandingly the torque required to separate the hook 1. 
Finally, the adhesive film 4 is removed from the baseplate 2 by peeling off 
the adhesive film 4 in the direction of the plane of the bond. 
Subsequently the hook 1 can be bonded again without limitations.