Note: Descriptions are shown in the official language in which they were submitted.
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27025-128
A RACQUET
The present invention relates to a racquet, in particular a
squash racquet. As a rule, racquets of this ~ind have a
relatively large handle section and a strung frame that is
relatively small in proportion to the length of the racquet.
In known racquets of the type described in the introduction
hereto, in principle, the properties that are relevant for a ball ~ -
game, in particular, the elasticity of the handle section, ball
acceleration, and oscillation and damping behaviour, have been
controlled mainly by the material and cross-sections used in the
handle section, between the strung frame and the handle end
itself. Various materials have already been used in the
construction o~ racquets of this kind. In particular, it has
been the practice to build racquets of relatively low weight,
when a light racquet of this kind results in good racquet
acceleration but also in ball acceleration that is not entirely
satisfactory, to say the least. When this was done, light
racquet weight was achieved only in racquets with a small impact
surface.
When racquets were constructed in the past, there were frequent
attempts, particularly when producing tennis racquets, to
increase the inherent or characteristic frequency by using new
and lighter materials. In tennis racquets, an increase of the
inherent frequency of this kind was aimed mainly at ensuring a
higher level of arm protection in racquets. In the case of
squash racquets, because of the different dimensions and the
essentially lower weight of the racquets, the conditions that
apply to this kind of racquet are completely dlfferent, and a
simplQ alteration of the weight,lbrought about by the selection
o~ lighter and, iP nacessary, sti~er materials does not always
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of necessity lead to an improvement in playing characteristics.
Because of the relatively small impact surface, an important
prerequisite when designing squash racquets is that a high level
of orientation stability be ensured at higher ball acceleration,
even i~ the ball strikes the strung frame at different points.
:.
It is the task of the present invention to develop a squash -
racquet of the type described in the introduction hereto such
that it ensures improved ball acceleration at the highest level
of precision with respect to orientation and, at the same time,
imparts good playing characteristics. According to the present
invention, in order to solve this task, it i5 proposed that the
total weight of the racquet, when unstrung, be less than 165 g;
and that the racquet have a head weight of less than 83 g, and in
particular less than 78g. In this definition, head weight is
understood to be that weight which can be measured at the head
end as reaction force [bearing load] when the racquet is
supported at the handle end, with the racquet in a horizontal
position. A racquet whose head weight, measured in this way, is
greater than half tbe racquet weight must be considered as
slightly head-heavy: in contrast to this, racquet with a head
weight that is less than half the racquet weight, as measured by
this method, would have to be considered as handle-heavy. The
solution according to the present inventlon, when the racquet, in
the unstrung state, is designed to have a weight o~ less than 165
g, in particular less than 165 g, with a head weight that is less
than 83 g, means, in other words, that what is involved here is a
racquet that is almost balanced when strung. What is obtained by
doing this is a racquet with which rapid reaction play is made
possible since, because of the low racquet weight and the weight
distribution within the racquet, as proposed by the present
invention, the racquet can be moved towards the ball at much
greater speed. Racquets known up to now have used significantly
greater head weights in order to arrive at acceptable playing
characteristics. Even in the case o~ the extremely light
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racquets that have been known up to now, the head weights were
always much greater than the ma~imum head weight that is proposed
by the present invention and, in addition to significantly
heavier racquets, there are already racquets on the market which,
although distinguished by a total weight of less than 165 g, and
in particular less than 165 g, nevertheless also have a head
weight of much more than 83 g. The balance of the racquet that
is achieved by the combination proposed by the present invention
leads to a greater level of stability, despite the low racquet
weight, and to precise playing characteristics of the sort that
up to now could only be achieved with significantly heavier
racquets. At the same time, despite the low weight of the
racquet, much the same good ball acceleration has also been
observed; in this connection, it is advantageous that the
significantly lighter racquet as proposed by the present
invention be strung at much higher stringing forces. Whereas
conventional squash racquets are normally strung at approximately
12 kg, the racquet according to the present invention should,
advantageously, be strung at approximately 14 kg.
According to a preferred embodiment, the configuration i5 such
that the racquet has an impact surface of no less than 330 cm2,
and in particular at least 350 cm2. Using a large-area racquet
of this kind, which is of low weight, the advantages with respect
to ball safety and acceleration are greater.
An additional and obvious improvement of playing characteristics
and, in particular, an especially high level of ball acceleration
can be achieved according to the present invention in that the .
moments of inertia at the handle end, in a plane that contains .
the stringing and in a direction that is normal to this are :.
smaller than 30 gm2, and in particular smaller than 28.5 gm2.
The values proposed by the present invention thus lie clearly . .
below formerly known values, although initially it was ~eared
that smaller inertial moments of this kind could result in lower
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ball acceleration and lower impact precision or stability. Most
surprisingly, however, the opposlte was achieved, whereby a
significantly lighter squash racquet that can be rapidly
accelerated can be achieved while complying with the cumulative
conditions, together with the cond~tions for the upper limit of
the total weight and the head weig~t. When this is done,
determination of the inertial moments is effected while securing
the racquet at the handle end by measuring the pendulum move~ent
of the racquet during a movement in the plane that contains the
stringing and in a direction that is normal to the stringing
plane.
According to the present invention, within the context of the
conditions for designing the squash racquet, it is also
advantageous to comply with the conditions that for a racquet, in
an unstrung state, with a centre of gravity distance of less than
390 mm, as measured from the handle end, the ratio of the
unstrung racquet weight to the head weight is less than 2.07, and
the ratio of the centre o~ gravity distance to the unstrung
racquet weight is greater than 2.1, when it is preferable that
the centre of gravity distance of the unstrung racquet ~easured
from the handle end is between 340 and 380 mm. Finally, it is an
advantage that the ratio of head weight to inertial moment be
less than 2.81 in the plane of the stringing~ All of these
criteria have been shown to be particularly advantageous for :
achieving neutral playing characteristics and, taken together,
they result in a balanced, fast-accelerating squash racquet that
provides a high level of impact precision.
Compared to known racquet designs with relatively large strung
areas, the above-defined ratio of head weight to inertial moment,
measured, in each instance, on an unstrung racquet, results in a
more characteristic but relatively smaller difference to
corresponding values measured on known racquets which, however,
without exception differ from the object of the present invention
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with respect to their weights. Whereas correspondingly large-
area racquets can easily , without exception, be made with
significantly higher racquet weights and higher head weights, it
has, most surprisingly, been shown that the greatly improved
playing characteristics with respect to impact precision and
quick racquet acceleration as well as rapid ball acceleration,
which can be achieved by the present invention, can be achieved
only by keeping within clearly defined limits, such as, for
example, the upper limit for the head weight to the inertial
moment.
Since, all in all, as has been set out in detail above, it is
primarily the weight, the head weight, and the impact surface
that help improve racquet characteristics, other criteria that
make it possible to identify superiority with reference to the
quoted playing characteristics were also considered in detail.
In this way, it was determined that particularly favourable
properties can be achieved if the ratio of the strung area to the
inertial moment, measured normally to the plane of the stringing,
is greater than 14, and in particular greater than 15. The
proportional values that are cited are, without exception cited
as absolute numerical values, which when considering the physical
values used in each instance for forming the ratios, would
strictly speaking come to a corresponding dimension. All known
designs with a racquet weight of less than 200 g have, most
surprisingly, resulted in a proportional value of at most 13.5 as
the upper limit, which in the fact means that the proportional
figure of greater than 14, determined according to the present
invention, has to be evaluated as being significant for the
improvement that can be achieved with relation to playing
characteristics. This applies, in particular, in the case of the
preferred minimum value for the ratio of strung area to inertial
moment of 15. Similarly, during investigation of the racquet
according to the present invention, it was determined that the
ratio of strung area to head weight is advantageously greater
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than 4.5, and preferably greater than 5.2. Here too, it has been
found that particularly with reference to the preferred value of
at least 5.2, a high value of this kind is not achieved by any of ~.
the known large-area squash racquets, so that in combination with
the conditions referred to above with respect to racquet weight,
head weight, and/or the impact surface, this value has to be
assessed as characteristic. .
