Note: Descriptions are shown in the official language in which they were submitted.
CA 02232854 1998-03-23
MIXING DEVICE
Background of the Invention
The present invention relates to a mixing device comprising
a swing arm for receiving a mixing capsule within securing arms
whereby at least one securing arm is movably supported at the
swing arm so that the two securing arms can be moved relative to
- one another.
Such a mixing device is, for example, known from U.S.
Patent 3,749,371. This document shows a mixing device with two
spaced apart securing arms which support the mixing capsule that
contains the dental material to be mixed.
Mixing capsules for dental materials are manufactured with
different dimensions, and the respective mixing devices therefore
require a spring-loaded support within the swing arm. Since the
- capsules are subjected to very high acceleration forces in order to
ensure a sufficient mixing action of the amalgam, the prongs of
the mixing device in the known device are thus subjected to high
loads so that they must be embodied with sufficient stability in
order to prevent breakage during operation. This requires that for
the insertion of the capsules relatively great actuating forces must
be expended.
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Furthermore, mixing devices have been suggested in which
- the mixing capsules are received in a closed space and are thus
securely contained. In this context, it has been suggested to
introduce by movement of one of the securing arms a canting
action in order to ensure a safe securing of the mixing capsule by
canting. In this suggested solution it is especially
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disadvantageous that the canting can act only on one side so that
during the return swing movement the canting force is greatly
reduced, if not eliminated. The canting elements are thus
subjected to great changing loads. The resulting corresponding
wear can not ensure safe canting over an extended period of time.
A further example of such a mixing device is known from
German Offenlegungsschrift 27 45 476 in which the mixing
capsule is secured in a closed chamber and a locked by a fork in
the mixing position. Even though this solution exhibits reduced
wear, it has not found acceptance because it requires a very
stable embodiment of the securing arm similar to the
aforementioned solution.
Since the securing arm swings or pivots, it is therefore not
only necessary to increase the drive forces in order to ensure the
same mixing result. Also, a stronger swinging load of the drive
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device results so that correspondingly strong oscillations,
undesirable in dental practices, are introduced into the
support of the mixing device.
Accordingly, -_n general, the comparatively light-
s weight spring-loaded mix_Lng devices or forks have found greater
acceptance whereby preferably hard and at the same time light-
weight spring steel has been used for the mixing forks. A
lateral introduction of the capsule is generally preferred. An
example for such a solut=ion is known from German Patent 41 06
388.
It is therefore an object of the present invention to
provide a mixing device of the aforementioned kind which, in
comparison to the prior <~rt mixing devices, introduces a
reduced amount of oscil7_ations into the support for the mixing
device but still ensure: easy operation with secure hold of
mixing capsules of different sizes.
Summary of the Invention
The invention provides a mixing device comprising: a
swing arm having a pivot, point at one end; a pair of securing
arms for receiving and securing a mixing capsule within said
mixing device, the securing arms being connected to the other
end of the swing arm for movement between an open capsule-
receiving position and a closed capsule-securing position, the
securing arms including at least one moveable securing arm that
is moveably secured to ~>aid swing arm; and an inertia mass
carried by the swing arm between the pivot point and the
moveable securing arm and acting via said at least one moveable
securing arm to secure t:he mixing capsule in said securing
arms.
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Advantageously, the swing arm is a mixing fork
comprising two prongs forming the securing arms, wherein one of
the prongs is pivotally supported to form the moveable securing
arm, and wherein the inertia mass acts onto the moveable
securing arm.
Advantageously, the mixing device further comprises
abutments, wherein the two prongs are elbow levers, wherein the
inertia mass acts on the two prongs, and wherein the abutments
limit a movement stroke of the elbow levers.
The securing arms are one-armed levers and a
centrifugal force generated by the inertia mass acts onto the
mixing capsule in a 1:2 reducing ratio.
The mixing device further comprises a pressure spring
positioned in the swing arm, wherein the swing arm has a pivot
bearing and wherein the pressure spring is positioned between
the inertia mass and the pivot bearing.
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Advantageously, the securing arms have cup-shaped
securing areas facing one another and the cup-shaped securing
areas receive end faces of the mixing capsule.
The mixing device further comprises abutments for limiting
a movement stroke of the securing arms, wherein, for receiving
the mixing capsule, the securing arms are moved away from one
another against the abutments so as to have a spacing there-
between that allows snapping the mixing capsule into the securing
areas with a brief spreading of the securing arms without having
to move the securing arms farther apart.
A securing force of the securing arms is selected such that
a sum of forces generated by the inertia mass and the pressure
spring is substantially greater than the centrifugal force of the
heaviest mixing capsule to be used with the mixing device.
- Advantageously, one of the securing arms is a hook that
compensates the centrifugal force of the mixing capsule and
another one of the securing arms is a clamping element for the
mixing capsule acting radially outwardly, wherein the inertia mass
is positioned in the clamping element.
The mixing device may further comprise a pressure spring
for pressing one of the securing arms against the mixing capsule.
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The securing arms are preferably connected to a common
pivot axis.
Advantageously, one of the securing arms is fixedly
connected to the swing arm, is hook-shaped, and laterally
supports the mixing capsule, the one securing arm having a U-
shaped depression for receiving the mixing capsule.
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The one securing arm supports end faces of the mixing
capsule.
Surprisingly, the inventive mixing device provides the
possibility to ensure with comparatively minimal weight a positive-
locking support of the mixing capsule. The inertia mass, which is
forced outwardly by the centrifugal force, results in a dynamic
increase of the securing force so that the securing force present
at rest can be selected to be rather small. This simplifies removal
from and loading of the mixing device. The inventive mixing
device allows a precise guiding of the securing arms which is not
cancelled even when the pivot movement (swing action) is
- combined with a wobble movement. The securing force is
greatest when the greatest centrifugal force acts on the mixing
capsule.
The inventive solution preferably suggests abutments which
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limit the movement of the securing arms. The spacing between
the securing areas, respectively, the receiving opening is then
somewhat smaller than the smallest capsule to be inserted so that
the abutments cannot impede the action of the inertia mass and
of the spring in any of the operating states but facilitates the
introduction of the mixing capsule.
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Preferably, a pressure spring is positioned between the
inertia mass and the securing arm. It enhances in a simple
manner the action of the inertia mass in the rest position of the
mixing device. Preferably, the pressure spring is guided in a
tubular securing section of the securing arm and has a spring
action acting in the direction of the securing arm. In this design
the last windings of the pressure spring enhance the action of the
inertia mass so that the size of the inertia mass can be further
'- reduced. Furthermore, the tubular design of the securing section
provides for a comparatively simplified construction whereby it is
understood that preferably high quality materials are used for the
mixing device.
Brief Description of the Drawings
The object and advantages of the present invention will
appear more clearly from the following specification in conjunction
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with the accompanying drawings, in which:
Fig. 1 is a schematic view of a mixing device in a first
embodiment of the invention;
Fig. 2 is a schematic view of the inventive mixing device in
a second embodiment of the invention;
Fig. 3 is a plan view of the mixing device in the embodiment
- according to Fig. 2.
Description of Preferred Embodiments
The present invention will now be described in detail with
the aid of several specific embodiments utilizing Figures 1-3.
The mixing device 10 represented in Fig. 1 comprises in a
first embodiment a swing arm 12 which is supported in a manner
known per se by a pivot bearing 14, as, for example, shown in
German Patent 41 06 388, and further comprises two securing
arms 16 and 18 connected to a pivot joint 20. The pivot or swing
action is carried out in the direction of arrows 22 so that in this
embodiment the axis of the pivot joint 20 extends substantially
parallel to the axis of the swing arm 12.
According to a modified embodiment, it is suggested that
the pivot axis extends at an angle of 90° relative to the non-
represented swing axis, i.e., it extend substantially parallel to the
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plane of the drawing.
The swing arm 12 comprises an inertia mass 24 which is
slidably supported in a tubular securing section of the swing
arm 12. The- inertia mass 24 comprises in the represented
embodiment two sockets 28 and 30 that extend laterally outwardly
and act onto the securing arms 16 and 18. The securing arms 16
and 18 are elbow joints, both supported at the pivot joint 20. In
the manner of a one-armed lever the action of the inertia mass 24
acts onto the securing arms 16 and 18 so that they move with
their cup-shaped securing areas 32, 34 toward one another.
Accordingly, a mixing capsule 36 received therebetween is
clamped by the action of the inertia mass 24, enhanced by the
action of the spring 38.
The securing arms 16 and 18, in the manner of a mixing
fork 40, have prongs 42 and 44 which form the securing areas 32
and 34.
Preferably, the mixing capsule 36 is secured with its end
faces in the securing areas 32 and 34 whereby, depending on the
position of the securing arms, greater or smaller mixing capsules
can be received. According to an alternative embodiment, it is
suggested that the securing arms 16 and 18 laterally suppon: the
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mixing capsule.
When the mixing device 10 is at rest, tha prongs 42 and 44
can be spread counter to the action of the pressure springs 38 in
order to insert ~r remove the mixing capsule 36 with the aid of its
slanted surfaces 45. The prongs 42 and 44 cannot come into
contact with one another because the action of the spring 38 is
limited by the abutments 46 and 48 which are connected to the
swing arm 12 and prevent that the pressure spring 38 acting on
the inertia mass 24 forces the elbow levers 16 and 18 towa; d one
another.
During mixing, a pivoting or swinging of the swing arm 12
about its pivot takes place. This movement
generates a centrifugal force for the inertia mass 24 in the
direction of arrow 50. Due to this centrifugal force, the securing
arms 16 and 18 are forced toward one another during mixing so
that the mixing capsule 36, which is also subjected to the
centrifugal force, is secured to an even greater extent in
comparison to the securing action by the spring 38 alone. The
sum of the forces of the inertia mass 24 and of the spring 38 is
such that even the heaviest mixing capsule 36 to be used with the
inventive mixing device can not spread apart the securing arms 16
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and 18.
A modified embodiment of the inventive mixing device can
be seen in Fig. 2. Same parts are identified with identical
reference numerals as in Figure 1. In this embodiment, which is
shown rotated by 90° relative to Fig. 1, the pivot action of the
swing arm 12 takes place about the pivot axis 52. The pressure
spring 38 is substantially longer than in the embodiment according
to Fig. 1. Accordingly, the windings of the spring remote from the
pivot axis 52 enhance the action of the inertia mass. In this
embodiment, the two securing arms 16 and 18 are asymmetrical
to one another, whereby the securing arm 16 engages about the
mixing capsule 36 which is received in the U-shaped depression
54 of the securing arm 16 while the securing arm 18 presses onto
the mixing capsule 36 from the opposite side. The securing arm
18 thus comprises the inertia mass 24, and the pressure spring 38
acts onto the arm 18 which is also partially used as an inertia
mass.
As can be seen in more detail in Fig. 3, the securing arm
16 secures the mixing capsule 36 at its end faces 56 and 58.
This design allows the use of a comparatively minimal weight for
the inventive swing arm 12, especially since the central area of
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the mixing capsule 36 is not supported as in the embodiment
according to Fig. 1 and is not covered by a portion of the swing
arm 12.
The securing arm 18 in the embodiment according to Figs.
2 and 3 is a plate supported by a pivot joint 20. The U-shaped
depression 54 is limited at one side by the plate that is positioned
at a slant relative to the depression 54. Due to this embodiment,
the insertion of the mixing capsule 36 is facilitated so that even a
one-hand operation of the inventive mixing device is possible.
Preferably, the securing arm 18 is limited by a non-represented
abutment in its movement in the direction of arrow 50 so that the
two securing arms 16 and 18 in this embodiment can also not be
moved too far apart.
According to a modified embodiment, an additional inertia
mass 24 is provided between the pressure spring 38 and the
securing arm 18. It further increases the securing force for the
mixing capsule 36. Due to the one-sided support by the corner
areas 60 and 62 of the securing arm 16 positioned opposite the
securing arm 18, the required securing force is comparatively
minimal so that it is preferred to use the securing arm 18 only as
an inertia mass 24.
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The pivot joint 20 in the embodiment according to Figs. 2
and 3 can be embodied in any desired manner. For example, it
is possible to provide thereat abutments of the securing arm 16
and thus of the swing arm 12 which have a pivot joint character
for the securing arm 18. In this embodiment, it is ensured by
correspondingly laterally arranged abutments thatthe plate-shaped
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'f securing arm 18 can not deflect laterally. ,
The present invention is, of course, in no way restricted to
the specific disclosure of the specifications, and drawings, but also
encompasses any modifications within the scope of the appended
claims.
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