Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 215818~1
The invention relates to a process for the regulation
in stages of the turning behaviour of a turntable
provided with a bearing platform and a turning
platform, along with the turntable itself.
A turntable of this kind is known from US-A-5,000,513.
The turning platform is held rotatably in position in
its central area by means of a bearing attachment on
the bearing platform and is supported outside this
bearing area on the bearing platform by an annular
surface. Between the turning platform and the bearing
platform there is a sliding connection. Such turntables
are used just as much by light persons as they are by
heavy persons. Since the turning force is a function of
the load, a light person requires only a small turning
force whereas a heavy person requires a much greater
turning force. In the known turntable, the frictional
pairing connection has a preset coefficient of friction
which is set for a person of average weight. For light
persons the turntable therefore moves too easily,
whereas the reverse is the case for heavy persons.
The ease of movement of the turntable can be increased
by the incorporation of anti-friction bearings, as is
known for example from US-A-2,757,388, which would
represent an improvement for heavy persons. However,
such a turntable would be unsuitable for light persons,
since handicapped persons are able to control their
movements only to a limited extent and the precise
regulation of a very slight turning force is often too
difficult a task for them. For light persons that
turntable gives rise to anxiety and lack of confidence.
The objective of the invention is to design a turntable
of the type initially described, in such a way as to
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allow the turning behaviour to be adjusted in simple
fashion to individual requirements.
This objective is achieved with a process of the type
described at the outset, by a arrangement as follows:
in a first stage the turning platform is supported on
the bearing platform by at least one annular surface on
the lower side, in a second stage a freely rotatable
ring element is inserted into at least one ring groove
in one of the surfaces of the two platforms facing
towards each other, which ring element has upper and
lower sliding surfaces with low coefficients of
friction and whose thickness measured axially is
greater than the depth of the ring groove, so that the
turning platform is supported on the bearing platform
only by this ring element, and the ring element has
several openings into which in a third stage rollers
are inserted in easily rotatable fashion, the effective
diameter of which rollers is larger than the effective
thickness of the ring element, so that the turning
platform is supported on the bearing platform only by
the rollers and the ring element operates solely as a
guide retainer for the rollers.
There is a turntable known from US-A-2905229 which has
ring grooves facing each other in the turning part and
the bearing part and a retainer with rollers inserted
into these grooves, but that document does not contain
any suggestion of also using the retainer as a sliding
element without the rollers.
The turntable according to the invention provides, in
terms of the stated objective, several possibilities
for changing the turning resistance. For particularly
light persons the ring element can be removed, so that
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the turning platform slides directly on the bearing
platform, as in the known turntable. This arrangement
provides the highest turning resistance. In the next
adjustment stage the turning platform slides on the
ring element, which in turn slides on the bearing
platform. Owing to the ease of movement of the ring
element in the ring groove of the turning platform
and/or the bearing platform there can be relative
sliding movement between the turning platform and the
ring element or between the ring element and the
bearing platform, or between both pairings of sliding
surfaces. This arrangement provides reduced turning
resistance. A further reduction in the turning force
required for operation is achieved by the insertion of
rollers into the openings in the ring element. Because
of the size of the diameter of the rollers in relation
to the thickness of the ring element, the sliding
movement is replaced by a rolling movement, leading to
a further reduction in the turning resistance. It is
important to note that when rollers are used the ring
element is now only acting as a retainer, and hence no
longer has any frictional effect on the turning
platform. If such rollers are used, the turning speed
of the ring element is one half of that of the turning
platform. The number of rollers used also has an effect
on the ease of movement of the turning platform. In the
case of a turntable with eight holes in the ring
element, a lesser degree of ease of movement than when
eight rollers are used can be achieved by the use of
four rollers; this represents the stage with the lowest
turning resistance. Hence the turntable according to
the invention has a minimum of three adjustment stages,
or if desired four, five or six adjustment stages for
the turning resistance, so that the most suitable
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turning resistance can be set in each individual case
according to the user's requirements.
The scope of this invention also includes the sale of
the turntable without the inserted ring element or
without the inserted rollers and the supply of the ring
element and/or the rollers in an accessory kit or the
subsequent supply of these items when requested, when
increased ease of movement is required. An essential
aspect of the invention is the presence of at least one
ring groove for the insertion of the ring element and
openings in the ring element for the insertion of
rollers, which may take place at a later time.
A further development of the invention consists in the
sliding surfaces of the ring element being formed on
narrow projections projecting upwardly and downwardly
from the ring element. This admittedly increases the
surface loading on the narrower sliding surfaces,
although it has little or no effect on the turning
resistance; however, cavities are created between the
projections which are used to provide space for dust
particles and foreign bodies penetrating into the
device. If the projections, according to a preferable
configuration, are arranged in two groups of ridge
formations intersecting at right-angles, with one pair
of linearly arranged projections in each of the groups
being placed radially with respect to the turning axis
of the turning platform, according to a conceivable
arrangement of annular projections this would result in
no slide paths being formed on the opposite flat
sliding surfaces of the turning platform and the
bearing platform.
The holes have retention tabs on one pair of facing
upper edges and one part of facing lower edges, which
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tabs cover the rollers in question from above and below
and prevent them from falling out, with the retention
tabs on at least one edge pair being capable of being
distorted in elastic fashion for the insertion and
removal of the rollers. Hence pressing with a finger on
each roller is all that is required to press the roller
into the hole in the ring element and conversely to
press the roller out from the element again.
According to a further development of the invention the
rollers, with the exception of their end faces, are
cylindrical and the holes are provided in rectangular
form in the radial section of the ring element, with
the rollers being accommodated in the holes with some
rotatory play.
The ring groove for the ring element can be provided as
preferred on the bottom of the turning platform or on
the top of the bearing platform, and it is also
possible to provide ring grooves fitting each other in
both platforms.
The invention is now described in more detail with
reference to the drawing, which represents one
embodiment example.
FIG. 1 shows a cross-section through the new
turntable,
FIG. 2 shows a top view of a ring element
incorporated in the turntable,
FIG. 3 shows a larger-scale view of detail X in
Figure 2,
FIG. 4 shows a cross-section along line A-A in
Figure 3, and
FIG. 5 shows a cross-section along line B-B in
Figure 3.
2 ~ 4
A turntable 10 consists of a circular disk-shaped
turning platform 12, a bearing platform 14, which is
also illustrated in this instance in a circular disk
shape but could also be oblong in shape, a layer of
padding 16 on the turning platform 12, a retention ring
18 clipped onto the outer edge of the turning platform
12 and extending over the outer perimeter of the layer
of padding 16, and a central bearing supporting the
turning platform 12 rotatably on the bearing platform
14, which central bearing consists of a turning
platform plug 22 and a bearing platform socket 24,
which engage by a form-fitting arrangement and are
joined together by a screw.
On its bottom side the bearing platform 24 has a
circular rubber strip which increases the purchase on a
base. On the bottom side of the turning platform 12
there are a number of ring-shaped supporting surfaces
28, 30, 32 by which the turning platform 12 can in some
circumstances be supported on the bearing platform 14
which is flat on its upper side, specifically when the
sliding and/or roller arrangement illustrated as 34 in
FIG. 1 is not provided or has been removed from the
turning platform 12.
on its bottom side the turning platform 12 has a ring
groove 36 in which a ring element 38 with radial
running gaps is lodged in rotatable fashion, coaxially
with respect to the turning axis 40 of the turning
platform 12. The thickness of the ring element 38 is
slightly larger than the depth of the ring groove 36,
so that upper and lower sliding surfaces are formed on
the ring element 38, which sliding surfaces form
sliding surface pairs with the bottom surface of the
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ring groove 36 on the one hand and with the upper
surface of the bearing platform 14 on the other.
These pairs of sliding surfaces have a low coefficient
of friction, so that the turning resistance of the
turning platform 12 is less when the ring element 38 is
used than without the said ring element 38.
The ring element 38 has two groups of projections 40,
42, intersecting with each other, projecting
respectively from the upper and bottom surfaces, on
which projections sliding surfaces 44, 46 are formed in
parallel radial planes. The projections 40, 42 bound
flat chambers in which dust particles and similar can
collect.
The ring element 38 has eight openings 48, arranged
radially at equal peripheral intervals, of rectangular
cross-section which can be but are not necessarily used
to accommodate cylindrical rollers 50. The rollers 50
are placed in precise radial fashion in relation to the
turning axis 40 of the ring element 38 and are arranged
in easily rotatable fashion in the openings 48. The
diameter of the rollers 50 is slightly larger than the
effective thickness of the ring element 38, as measured
between the two parallel planes in which the sliding
surfaces 44, 46 of the projections 40, 42 lie. This
excess of the roller diameter with respect to the
thickness of the ring element 38 can be so small that
the sliding friction between the sliding surfaces 44 on
the lower surface of the ring groove 36 and the sliding
surfaces 46 on the upper surface of the bearing
platform 14 is merely decreased but not eliminated, so
that the loading on the turntable 10 is distributed
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over both the rollers 50 and the sliding surfaces 44,
46.
It is therefore quite clearly within the scope of the
invention to have two sets of roller sizes issued
separately as accessories for the turntable 10, with
the set of rollers with the smaller diameter to be used
when a combined sliding and rolling bearing arrangement
is desired. The set of somewhat larger rollers 50 would
then be used to eliminate the sliding friction, so that
the ring element 38 in that case would be acting solely
as a retainer for the rollers and on the rotation of
the turning platform 12 under load would merely rotate
with the platform, without transferring any force to
the bearing platform 14. In this instance the ring
element 38 turns half as quickly as the turning
platform 12, ie on a 900 rotation of the turning
platform 12 the ring element 38 would complete a
rotation of only 450.
On the lower edges of each opening 48 there are tabs 52
running along the central sector of the holes 48 which
secure the rollers 50 from below. At both ends of the
upper edges of the openings 48 similar tabs 54 are
formed, covering the rollers 50. These tabs 52, 54 are
capable of being distorted in elastic fashion, so that
the rollers 50 can easily be pressed by the pressure of
a finger into the holes 48 and can also be pushed out
again. It is self-evident that the rollers 50 between
the pairs of tabs are free to roll on the surfaces of
the turning platform 12 and the bearing platform 14, as
applicable.
In the embodiment example eight holes 48 are provided,
so that on the insertion of a roller 50 in each of
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these openings a very low turning resistance for the
turntable 10 will be achieved. This allows comfortable
rotation with little force in the case of loading with
a heavy person. If the turning resistance is to be
increased, in a first increased resistance stage the
number of rollers 50 can be halved by the removal of
every second roller. In the next stage of increased
turning resistance these remaining rollers 50 are also
removed, so that the ring element 38 then loses its
guide function as the retainer for the rollers and
acquires a support function in the form of a sliding
ring. If the turning resistance of the turntable 10 is
still too high for the required use in the specific
situation in question, the ring element 38 is
completely removed from the recess 36, so that the
difficulty of movement now necessarily involved in the
turning of the turntable 10 is appropriate for
particularly light persons.
