Note: Descriptions are shown in the official language in which they were submitted.
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Screwdriver
The invention concerns a screwdriver according to the preamble of
claim 1.
Screwdrivers of this type have a polygonal contact zone which is
usually in the form of a hexagonal contact zone. The contact zone
in socket screw wrenches is in the form of a polygonal cylinder and
in ball end screwdrivers in the form of a polygonal ball. The
screwdrivers can be furnished with a handle or be in the form of an
offset screwdriver. It is also possible to make it in the form of
a screwdriver insert which can be fitted into a screw tool.
In the known screwdrivers, the contact zone of the tip grips into
the inner polygon of the screw with more or less little play. As
a result, the screw does not have a f irm hold on the tip of the
screwdriver which is disadvantageous when the screw has to be
screwed in or out at a difficult-to-access location, so that it
cannot also be held.
The object of the invention is to provide a screwdriver of the
aforementioned type in which a screw can be held at the tip.
According to the invention, this object is solved by a screwdriver
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having the features of claim 1.
Advantageous embodiments and further developments of the invention
are noted in the subclaims.
The basic idea of the invention lies therein that at least one
clamping element be placed in the contact zone of the tip of the
screwdriver which protrudes beyond the outer contour of the contact
zone and fits against the inner polygon of the screw under elastic
force. When inserting the tip of the screwdriver into the inner
polygon of the screw, a frictional connection is established
between the screwdriver and the screw by means of the clamping
element, as a result of which the screw is held firmly at the tip
of the screwdriver. The elastic flexibility of the clamping
element thereby makes it possible to push the clamping element back
against the outer contour of the contact zone and preferably into
it. Thus, the clamping element does not hinder the form-locking
engagement with slight play of the contact zone in the inner
polygon of the screw which is necessary for a good torque
transmission from the screwdriver to the screw.
To enable an engagement of the contact zone of the tip in the inner
polygon of the screw which is as free of play as possible for an
optimal torque transmission, the at least one clamping element is
preferably situated in a recess of the surface of the contact zone.
As a result, the clamping element can be completely pushed into the
recess, so that the form-locking and the torque transmission are
not affected vis-a-vis conventional screwdrivers.
The clamping element can be made in various ways. It is essential
that it protrudes beyond the surface of the contact zone of the tip
to such an extent that it can fit against the inner polygon of the
screw under elastic force and that it can be pushed back against
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the outer contour or into the outer contour of the contact zone to
such an extent that it does not hinder an optimal form-locking of
the contact zone with the inner polygon for the torque
transmission.
Preferably, a synthetic material that is elastically compressible
is used as clamping element. It is also possible to make the
clamping element from an incompressible, elastically workable
material, preferably of metal, whereby the working results in a
turning aside of the clamping element into the outer contour of the
contact zone. Finally, it is also possible to use a rigid clamping
element which protrudes beyond the surface contour of the contact
zone loaded by a spring and pressed into the surface contour by the
force of the spring. Which design of the clamping element is
preferred depends on the required clamping force, the required
resistance to wear and on the required manufacturing costs.
The clamping elements may be in the form of point-like protrusions,
e.g. in the form of plastic studs or spring-loaded balls.
Preferably, the clamping elements are made linear, as a result of
which an improved form-locking connection can be produced. The
linear clamping elements can thereby extend in peripheral direction
or in axial direction. If clamping elements extending in axial
direction are provided, then several linear clamping elements are
preferably arranged at equal angular distances vis-~-vis one
another, as a result of which a form-locking connection distributed
uniformly over the periphery is produced as with clamping elements
extending in peripheral direction.
The invention shall be described in greater detail in the following
with reference to the embodiments illustrated in the drawings,
showing
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Fig. 1 a first embodiment of the invention in a lateral view
(a), a section along the line A-A (b), a view in
direction B (c) and in a section along the line C-C,
Fig. 2 a second embodiment of the invention in a lateral view
(a), in a section along the line A-A (b) and in a section
along the line B-B (c),
Fig. 3 a representation corresponding to Fig. 2b of a third
embodiment of the invention and
Fig. 4 a fourth embodiment of the invention in a representation
(a) corresponding to Figures ld and 2c and an enlarged
detail (b).
The tip of a screwdriver is shown in Fig. 1, the contact zone of
which is in the form of a hexagonal ball end 10.
Recesses 12 are worked into each of the six surfaces of the ball
end 10, said recesses proceeding together from the front apex of
the ball end 10 and extending in a straight line in axial
direction, always in the centre of the hexagonal surfaces. The
recesses 12 extend in axial direction up to the area of the ball
end 10 with the largest diameter. Clamping elements which are in
the form of plastic strands 14 are arranged in the recesses 12. As
is shown especially in Figures lb and ld, the plastic strands 14
each have a somewhat circular cross-section, whereby one part of
the cross-section of the plastic strands 14 lies in the recesses
12, while the other cross-sectional part protrudes beyond the
surface contour of the ball end 10 with a measurement X. The
length of the plastic strands 14 corresponds to the axial length of
the recesses 12. The plastic strands 14 merge in the front apex.
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The plastic strands 14 consist of an elastically compressible
synthetic material, e.g. of polyurethane or TPE (thermoplastic
elastomers) or also of other elastic materials, such as e.g.
adhesives. The plastic strands 14 are applied by injection
molding, vacuum molding or by immersing the ball end 10. The
plastic strands 14 are held in the recesses 12 by contact adhesion.
It is also possible to make the recesses 12 with an undercut cross-
section, so that the plastic strands 14 are also held in a form-
closed manner.
The measurement X with which the plastic strands 14 protrude beyond
the surface of the ball end 10 is somewhat greater than the play
that remains between the surface of the ball end 10 and the inner
hexagonal surface of the screw when the ball end 10 is inserted
into the inner hexagon of a screw. When inserting the ball end 10
into the inner hexagon of the screw, the plastic strands 14 are
then elastically pressed together and fit against the inner
hexagonal surfaces of the screw under the action of their elastic
restoring force. As a result, a tensional clamping results between
the hexagonal ball end 10 and the screw by means of which the screw
is held at the ball end 10. Since the plastic strands 14 can also
be compressed into the recesses 12, the closed shape required for
the torque transmission between the hexagonal ball end 10 and the
inner hexagon of the screw is not affected by the plastic strands
14.
Fig. 2 shows a second embodiment of the invention with a hexagonal
ball end 10.
In this embodiment, a recess 12 extends in peripheral direction of
the ball end 10 in the area of the largest diameter of the ball end
10. The recess 12 may be made as a perforation in the ball end 10,
so that the base of the recess 12 is circular in cross-section
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(Fig. 2b). A plastic strand 14 is inserted into the recess 12, the
cross-section of said plastic strand being essentially circular.
The depth of the recess 12 and the diameter of the plastic strand
14 are adjusted to one another in such a way that the plastic
strand 14 extends beyond the surface of the ball end 10 with a
measurement X in the area of the hexagonal surfaces of the ball end
10, while the edges of the ball end 10 radially protrude for their
part beyond the plastic strand 14.
In this case also, the plastic strand 14 may consist of a suitable
elastomer material which is fastened in a self-holding, self-
adhesive manner or by an adhesive and inserted into the recess 12
by injection molding, vacuum molding or immersion. In this
embodiment, it is also possible to make the plastic strand 14 as a
prefabricated O ring which is then mounted on the ball end 10 and
lodges in the recess 12.
Fig. 3 shows a variation of the embodiment of Fig. 2. The ball end
and the recess 12 correspond to the embodiment of Fig. 2.
However, in this case, a spring steel ring 16 is placed into the
recess 12 as clamping element. The spring steel ring 16 is divided
like a snap ring, so that it can be pressed together against a
spring force while the diameter diminishes. The spring steel ring
16 may be made circular or may also be bent from a wire so as to
have a wavy annular shape, as shown in Fig. 3. The spring steel
ring 16 is dimensioned in such a way that it protrudes beyond the
surface of the ball end by the measurement X in the area of the
hexagonal surfaces of the ball end 10 when the tension is released,
while it is within the surface contour in the area of the edges of
'the ball end 10.
It can be readily seen that the embodiment of Figures 2 and 3, in
which the clamping element 14 or 16 is situated in a recess 12
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extending in peripheral direction, cannot only be used in a tip
whose contact zone is made in the form of a ball end, but also with
a polygonal socket screw wrench whose contact zone is made in the
form of a polygonal cylinder.
In the embodiments of Figures 2 and 3, the plastic strand 14 or the
spring steel ring 16 is also pressed together in radial direction
against an elastic restoring force when the ball end 10 (or the
cylindrical contact zone) is inserted into the inner hexagon of a
screw and fits against the inner surface of the inner hexagon of
the screw so as to be form-locked under the action of the restoring
force .
Fig. 4 shows a fourth embodiment of the invention in which the tip
of the screwdriver has a hexagonal cylindrical contact zone 18.
In this embodiment, the recesses 12 are radially arranged in the
plane front surface of the contact zone 18, as this corresponds to
the representation in Fig. lc, and lead in axial direction, always
in the centre in the hexagonal surfaces of the contact zones 18.
Plastic strands 14 made of an elastically compressible synthetic
elastomer material are inserted into the recesses 12 which come
together in the front surface in a star-shaped manner. The plastic
strands 14 are concentrated in the axially extending sections of
the recesses 12 in such a way that they protrude by a measurement
X beyond beyond the surface of the lateral surfaces of the hexagon
of the contact zone 18, as can be seen especially in Fig. 4b. The
plastic strands 14 do not completely fill the axially extending
sections of the recesses 12 up to their rear axial end, so that a
displacement space 20 remains free in the recesses 12 between the
axially rear end of the plastic strand 14 and the axially rear end
of the recess 12, as can be seen in Fig. 4b. The axial length of
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the recesses 12 in the lateral surfaces of the contact zone 18 is
shorter than the immersion depth Y with which the contact zone 18
sinks into the inner hexagon thereof when inserted into a screw.
If the tip of the screwdriver with the contact zone 18 is inserted
into the inner hexagon of a screw, then the plastic strands 14 are
elastically compressed in their areas protruding beyond the lateral
surfaces of the contact zone 18 and are preferably pressed into the
respective displacement spaces 20. Due to the elastic restoring
force of the elastomer material of the plastic strands 14, they fit
against the inner surfaces of the inner hexagon of the screw in a
form-locking manner and hold them to the tip of the screwdriver.
Since the immersion depth Y of the contact zone 18 is greater than
the axial length of the plastic strands 14, an area in which the
hexagonal contact zone 18 engages positively with the inner hexagon
of the screw without loss of torque is produced axially behind the
plastic strands 14.
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List of Reference Numbers
Ball end
12 Recesses
14 Plastic strand
16 Spring steel ring
18 Cylindrical hexagon
Displacement space
X Protrusion measurement
Y Immersion depth
