WINDSCREEN WIPER BLADE
This invention relates to a windscreen wiper, which is also
known as a windshield wiper. The invention also relates to a blade for
a windscreen wiper.
According to a first aspect of the invention, there is provided a
windscreen wiper, which includes
an elongate beam;
a blade having
a backing strip which is attached to the beam, the backing strip
having a substantially planar upper surface,
a wiping portion which has at least one wiping edge which, in
use, contacts a work surface to be wiped,
a plurality of hinges each defined by a suitably flexible web, with
a first hinge web being adjacent the backing strip and a second hinge
web being adjacent the wiping portion,
with each hinge web having an axis and with each hinge web
being able to flex between nominal limit positions on either side of its
axis, whereby the wiping portion is displaceable between nominal limit
positions on either side of the backing strip,
such that, at substantially any point along the length of the
blade, if the blade is displaced to pivot the wiping portion to one side,
CONFIRMATION COW
to its nominal limit position, the acute angle between a line between
the edge, or the edge which would contact the work surface with the
blade so displaced, and the axis of the first hinge web and a line which
extends substantially perpendicularly to the upper surface of the
backing strip is
less than 33° .
The said acute angle may be less than 30°, and preferably
the angle is less than 27 ° .
The blade may have two discrete hinge webs. The axis
of each hinge web may be centrally located and may be a hinge axis.
The blade may have an intermediate portion which is
located between the backing strip and the wiping portion, with a first
hinge web being between the backing strip and the intermediate portion
and a second hinge web being between the intermediate portion and
the wiping portion.
The intermediate portion may have a pair of laterally
extending body parts, each having an upper surface, which faces the
backing strip, and a lower surface, which faces the wiping portion.
The upper and the lower surfaces of the intermediate
portion may be substantially planar and may extend substantially
parallel to the upper surface of the backing strip when the blade is in
its unstressed form.
The backing strip may also have a pair of lower surfaces,
on each side of the first hinge web, which face the intermediate portion
and are spaced from the upper surfaces of the intermediate portion by
the first hinge web. The lower surfaces of the backing strip may be
planar and substantially parallel to the upper surface of the backing
strip.
The wiping portion may extend on both sides from the
second hinge web to have an upper surface on each side of the second
hinge web, which face the intermediate portion. The upper surfaces
of the wiping portion may also be planar and may also be substantially
parallel to the upper surface of the backing strip when the blade is in
its unstressed form.
It will be appreciated that the first hinge web will have a
suitable width (the distance from the backing strip to the intermediate
portion), the lower surfaces of the backing strip and the upper surfaces
of the intermediate portion will have a suitable breadth (the distance
from the first hinge web outwardly), to define the flexed nominal limit
positions of the intermediate portion relative to the backing strip. It will
further be appreciated that the second hinge web will also have a
suitable width, and the lower surfaces of the intermediate portion and
75 the upper surfaces of the wiping portion will have a suitable breadth,
to define the flexed nominal limit positions of the wiping portion relative
to the intermediate portion.
The beam may have a varying width and thickness. The
80 beam may be curved in a plane or may have compound curvature. In
a preferred embodiment of the invention, an upper surface of the
backing strip is secured to a bottom surface of the beam by means of
an adhesive material.
85 It will further be appreciated that, in use, the friction force
between the wiping portion of the rubber blade and the contact surface
when the blade is displaced relative to the contact surface causes
pivotal movement of the wiping portion. When the direction of
displacement changes, it is desired that the blade pivots to the other
90 side or "flips over", at the stage in its displacement relative to the
contact surface in the instant before the rubber blade starts to "flip
over" .
In use, at the stage of the windscreen wiper's
95 displacement relative to the contact surface, in the instant before the
rubber blade starts to "flip over", when the blade is displaced by means
of a force which is substantially parallel to its upper surface;
with the force of friction vector F(μ) extending substantially parallel to
the upper surface of the backing strip from the edge which contacts
100 the working surface;
with the normal force vector representing the force being exerted by
the surface on the rubber blade, F(v), extending substantially
perpendicularly to the upper surface of the backing strip; and
the resultant force vector F(R) extending between F(μ) and F(v),
105 the hinge axis of the first hinge web may be situated between the
vectors F(v) and F(R).
According to a second aspect of the invention, there is
provided a blade for a windscreen wiper, which includes
110 a backing strip which is attachable to the beam and which has
a substantially planar upper surface,
a wiping portion which has at least one wiping edge which, in
use, contacts a work surface to be wiped,
a plurality of hinges each defined by a suitably flexible web, with
115 a first hinge web being adjacent the backing strip and a second hinge
web being adjacent the wiping portion,
with each hinge web having an axis and with each hinge web
being able to flex between nominal limit positions on either side of its
axis, whereby the wiping portion is displaceable between nominal limit
120 positions on either side of the backing strip,
such that, at substantially any point along the length of the
blade, if the blade is displaced to pivot the wiping portion to one side,
to its nominal limit position, the acute angle between a line between
the edge, or the edge which would contact the work surface with the
125 blade so displaced, and the axis of the first hinge web and a line which
extends substantially perpendicular to the upper surface of the backing
strip is less than 33° .
The said acute angle may be less than 30°, preferably less
130 than 27° .
The blade may have two discrete hinge webs. The blade
may have an intermediate portion which is located between the backing
strip and the wiping portion, with a first hinge web being between the
135 backing strip and the intermediate portion and a second hinge web
being between the intermediate portion and the wiping portion.
The intermediate portion may have a pair of laterally
extending body parts, each having an upper surface, which faces the
140 backing strip, and a lower surface, which faces the wiping portion.
The upper and the lower surfaces of the intermediate portion may be
substantially planar and may extend substantially parallel to the upper
surface of the backing strip when the blade is in its unstressed form.
145
In use, when the blade is displaced by means of a force
which is substantially parallel to its upper surface;
with the force of friction vector F(μ) extending substantially parallel to
150 the upper surface of the backing strip from the edge which contacts
the working surface;
with the normal force vector representing the force being exerted by
the surface on the rubber blade, F(v), extending substantially
perpendicularly to the upper surface of the backing strip; and
155 the resultant force vector F(R) extending between F(μ) and F(v),
the hinge axis of the first hinge web may be situated between the
vectors F(v) and F(R) .
The blade may, conveniently, be of rubber which may be
160 synthetic or natural, or any other suitable material or combination of
materials. The blade may also be manufactured in an extrusion
process, in one piece.
The invention is now described, by way of example, with
165 reference to the accompanying drawings.
In the drawings,
Figure 1 shows a three-dimensional view of one end of a blade
for windscreen wiper in accordance with the invention; and
170 Figure 2 shows an end view of the wiper of Figure 1 , in use.
Referring to the drawings, a windscreen wiper in accordance
with the invention, is generally designated by reference numeral 10.
The wiper 10 includes an elongate beam 1 2 and a rubber blade
175 generally indicated by reference numeral 14.
The rubber blade 1 4 includes a backing strip 1 6 having a planar
upper surface 17 which is attached to the beam 12 by means of an
adhesive material. It also includes an intermediate portion 1 8 having
180 a pair of laterally extending body parts 1 8.1 and 1 8.2. The rubber
blade 14 further has a wiping portion 20 which tapers toward wiping
edges 22 which, in use, contact a surface 24 to be wiped at a point of
contact 26 (as shown In Figure 2) . A first hinge web 28 having a
centrally located first hinge axis 30 is defined between the backing
185 strip 1 6 and the intermediate portion 1 8 of the rubber blade 14. The
intermediate portion 1 8 is pivotal relative to the backing strip 1 6 about
the first hinge axis 30, between a first nominal limit position on one
side (as shown in Figure 2) where the body part 1 8.1 abuts the backing
strip 1 6 and a second nominal limit position on the other side. The
190 second limit position is not shown in Figure 2, but it will be appreciated
that the second limit position will be where the body part 1 8.2 abuts
the backing strip 1 6.
A second hinge web 32 having a centrally located second hinge
axis 34 is defined between the intermediate portion 1 8 and the wiping
portion 20 of the rubber blade 14. The wiping portion 20 is in turn
pivotal relative to the intermediate portion about the second hinge axis
34 between a first nominal limit position on one side (as shown in
Figure 2) where the body part 1 8.1 and the wiping section 20 abut and
a second nominal limit position on the other side. It will thus be
appreciated that the wiping portion 20 will be pivotal relative to the
backing strip 1 6 about nominal limit positions on either side.
As shown in Figure 2, if the blade 14 is displaced to pivot the
intermediate portion 18 and the wiping portion 20 about the first and
second hinge axes 30 and 34 respectively, to one side in the direction
of the arrow 38, to their respective nominal limit positions, the line 40
between the point of contact 26 and the first hinge axis 30 will
subtend an acute angle of about 30° with a line 46 that is
perpendicular to the upper surface 1 7.
In use, the wiping portion 20 is displaced to one side by friction,
the wiping portion 20 experiencing a friction force F( /) which is
dependent on the magnitude of the downward force exerted via the
beam 1 2 and the coefficient of friction ( /) . Thus, if the blade 14 is
pressed downwardly onto the surface 24 so that contact is established
between the wiping portion 20 and the surface 24 at the point of
contact 26, and displacement of the blade 14 relative to the surface is
changed from a first direction as indicated by the arrow 36 to the
opposite direction as indicated by the arrow 38, the point of contact
220 will experience a typical normal force F(v) represented by the vector 46
and a typical friction force F(μ) represented by the vector 44. The
resultant force, F(R), which is represented by vector 48 will subtend an
angle Θ with respect to the normal force F(v) which is then, typically,
about 30° . The angle between the lines 40 and 46 is 26,5 °, as
225 indicated in Figure 2. The applicant has found that the coefficient of
friction is usually greater than 0,6 although it can decrease to as low
as 0,5. Thus, if the angle a between the lines 40 and 46 is less than,
26,5 ° when the blade is deformed by the maximum expected down
force, then it can be expected to always "flip over" in use.
230