Note: Descriptions are shown in the official language in which they were submitted.
l 3~l /56
CONVEYOR SYSTEM WITH DRIVEN BALLS, PROTECTABLE AGAINST
OVERLOADING
The invention relates to a conveyor system with driven
balls in which each driven ball is supported by at least
one driving roller.
A system of this kind is described in EPA 180710, where
each driven ball is supported by a driving roller mounted
vertically below the centre of the ball. The full verti-
cal load of the balls must be taken up by the driving
roller and by the bearings in which this roller is suppor-
ted. This known conveyor system is exclusively suited to
the displacement of the goods in one direction.
The object of the present invention is to provide an
improved system of the kind mentioned hereinbefore, which
system is particularly suitable for the transportation and
assortment of goods in boxes or on pallets and the like,
whereby heavy loads can easily be taken up and the system
has an inbuilt protection against overloading, and whereby
it is moreover possible to improve the conveyor system in
a simple fashion to make it suitable for the displacement
of goods in different directions.
To achieve this object, it is proposed according to the
invention to position the point of contact between the
driving roller and the ball in a system of the kind
mentioned hereinbefore at some distance below the horizon-
tal plane of the ball, which distance is smaller than the
radius of the ball. In a few instances, driving rollers
may be positioned in the horizontal plane through the
centre of the ball. In a conveyor system designed along
3~
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these lines, the driven balls rest sideways against a
driving roller or, when several driving rollers are
applied, between the driving rollers. In consequence of
the wedge effect, a considerable driving force can thereby
be transmitted between the ball and the roller. Heavy
loads experience a greater driving force, light loads a
smaller one.
A further asset is that this ball drive can be rendered
safe: if humans, for instance, step onto a rotating ball,
this ball must stop. In actual practice it has been found
that, if both the ball and the rollers have been made of,
for instance, steel, both heavy and light loads can be
reliably moved and experience a sufficient driving force,
while the ball can still be stopped simply by hand or with
a shoe. This can be accounted for in the following way.
The drive force on the shoe or the hand depends not only
upon the vertical load on the ball but also upon the
coefficients of friction between the ball and the rollers
and between the ball and the shoe or hand. The coeffi-
cient of friction between the shoe or hand and the ball isfar greater than that between the ball and the roller
(both made of steel in the example). Without causing
injury or damage to hand or shoe, the rollers will then
slip and not drive the ball.
Furthermore, the system claimed in EPA 180710 is by nature
unstable: the balls must be maintained in position above
the drive shaft, which causes friction. The claimed
system supports the ball with stability.
In a preferred embodiment of the conveyor system according
to the invention, each driven ball is supported by four
driving rollers, i.e. two pairs of two rollers aligned in
parallel to each other, whilst provision has been made for
an independent drive unit for each pair of parallel
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driving rollers. Conveniently, adjacent bearings of a
driving roller of each pair may be located either in a
support rotating on a vertical axis or in a support which
is flexible in a vertical direction. Thereby, uniform
loading of the driving rollers and a simple safeguard
against overloading are achieved.
The use of two pairs of two driving rollers aligned in
parallel, each having its own drive unit, makes it possi-
ble to drive alternately one pair or the other. The
direction of the displacement of the goods induced by the
driven balls will thereby shift throuyh 90 degrees. This
shift is brought about because the effective radius of the
driving roller pair vis-à-vis the centre of the ball is
equal to the radius of the ball, whereas the effective
radius of the non-driving roller pair is considerably
smaller, so that the friction produced by this non-driving
roller pair can easily be overcome.
In another preferred embodiment of the conveyor system
according to the invention, each driven ball is supported
by three driving rollers in or near a horizontal plane.
These driving rollers are preferably positioned such
relative to one another that together they form an equila-
teral triangle and thus support the ball uniformly. In
addition, these driving rollers are provided with indepen-
dent drive units. By proper adjustment of the rotatingspeeds of the driving rollers it is possible to drive the
ball in arbitrary directions, enabling the load resting on
the ball to be propagated in all directions. The internal
friction in this system between the ball and the driving
rollers is at a minimum, if the rotating speeds of the
driving rollers is chosen such that the ball rotates on an
axis in the horizontal plane.
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It is to be noted that the German patent application
DT AS 1237003 describes a conveyor system with driven
balls where drive units are coaxially disposed in pairs
for selectively driving the balls under an axial thrust.
In this set-up, however, the driving force depends on the
axial force exerted, whilst the weight of the goods to be
conveyed plays no part.
Also, special provision must be made for the vertical
support of the balls.
10 The Netherlands patent application NL 7300241 claims
another conveyor system whereby the direction of transpor-
tation can be changed. In this design, each driven ball
rests upon a disc rotatable on a vertical axis which has
to take up the vertical load on the ball and which has to
be displaced in its entirety vis-à-vis the driven ball if
the direction of transportation is to be changed. In
addition, the balls naturally tend to lie unsteady and
need to be contained sideways to prevent them from rolling
away under the action of the load to be conveyed.
In a conveyor system according to the invention, a change
of direction can simply be effected by merely manipulating
the drive units of two, three or four driving rollers.
Depending on the driving velocities of the various driving
rollers, even the direction of transportation can be
chosen at will. Moreover, the balls rest naturally in
their places, lying consistently steady.
FR-A-2,192,050 describes a system in which each ball is
driven by four rollers aligned at an angle of 90 degrees
relative to one another, in which provision has been made
for independent drive units for each pair of rollers.
However, the ball must be supported precisely below the
centre and freely rotatable on a horizontal axis, because
the driving rollers are disposed in a plane whose level is
somewhat above the centre of the ball. The rollers must
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therefore be pressed against the ball by a separate contrivance,
as is the case in the aforementioned DT AS 1237003. The wedge
effect induced by the load is lacking. The compressive force for
assisting the drive and the support for the load are distinctly
separate functions in FR-A-2,192,050. The driving force is
therefore dependent not upon the load but on a mechanical setting.
Moreover, said conveyor system is unsafe if adjusted to heavy
loads.
In its broadest aspect the invention consists of a conveyor system
with driven balls, in which each driven ball is supported by at
least one driving roller, said driving roller having an axis which
is located in a substantially horizontal plane through the center
of the driven ball, and the driven ball is supported by freely
rotating element with the driven ball resting between the driving
roller and the freely rotating element.
The invention will now be elucidated in more detail for some
embodiments by way of example with reference to the accompanying
drawings, in which:
Figure 1 is a plan view of an embodiment of the conveyor system;
Figure 2 is a schematic representation of the rectilinear
displacement;
Figure 3 is a schematic representation of a provision against
overloading;
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- 5(a)
Figure 4 is a schematic representation of a four-point support;
igure 5 schematica].ly represents how a displacement in several
directions can be effected with the aid of a four-point
support;
igure 6 depicts a variant of the four-point support of Figure 4.
This variant features no intersecting shafts;
igure 7 is a schematic representation of a three-point support;
igure 8 schematically represents how several balls can simply be
driven simultaneously in the same direction;
igure 9 depicts a variant of the three-point support of Figure
7. This variant features fewer intersecting shafts;
igure 10 shows;
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Figure 9. This variant features no intersecting
shafts;
Figure 11 schematically represents how a rotary motion can
be effected;
Figure 12 shows an embodiment in which a ball is at all
times supported steadily with a drive in which
adjacent balls are interconnected;
Figure 13 shows an example of how protection against
overloading can be attained in a support;0 Figure 14 shows an example of how protection against
overloading can be attained in a roller; and
Figure 15 shows an example of how protection against
overloading can be attained in a cone-shaped
roller.
By way of example, Figure 1 shows the embodiment of a
conveyor system in which a side-track C is diverted from a
main track A-B. The supply and delivery tracks may, for
instance, be line-roll conveyors or conveyor belts (such
as B and C). Component part A in the supply track and
part D at the point of intersection of these tracks are
the subject of this patent application. It is in these
parts that the goods to be displaced rest on an adequate
number of balls 1, which are each supported at the bottom
side in such a manner that they can be driven in the
desired direction and with the desired velocity. The
whole is closed by a cover plate 5 through which the balls
1 project to a sufficient level.
Figure 2 relates to part A and is a sectional side view,
showing how each ball must be supported for a rectilinear
movement and how the goods 3 are set in motion through the
driving force exerted by rollers 2. The ball can be
prevented from slipping away sideways by, for instance, a
smooth plastic ring 4 or smooth plastic abutments 29
fitted approximately level with the rollers 2. This
arrangement makes it possible to produce great driving
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forces compared with the frictional forces exerted by the
lateral support. The farther the rollers 2 are placed
apart, the more heavily they press against the ball 1.
Hence, the tendency to slip drops and the stability in the
direction of drive increases. In addition, the balls tend
progressively less to slip away under the action of the
load to be displaced. On the other hand, the friction
forces have a minimum effect, inasmuch as they
- are relatively small, because they are only produced
by the tendency to roll away sideways;
- engage on a smaller radius r, compared with the
radius R upon which the driving forces act.
Figure 3 indicates that it suffices in the event of
overloading to make a roller 2 yield flexibly, in order
that a support 6 disposed below the ball 1 may absorb the
overloading. It is recommended to provide the centre of
the support 6 with a drainage slit 7.
Figure 4 relates to part D and is a sectional side view,
showing how the ball 1 must be supported for a displace-
ment at right angles. The ball now rests, its weight
uniformly distributed, on four rollers 2.1 and 2.2, which
may be driven in pairs. The points of contact between the
driving rollers and the ball lie in the vertical plane at
an angle alpha relative to the horizontal. This angle may
vary from 2Q to 70 degrees, but lies preferably between 25
and 35 degrees. By actuation of the rollers 2.1 the goods
may be moved from left to right in the drawing. Actually,
the ball also rests on the rollers 2.2, but friction with
the rollers 2.2 will not impede rotation, because the
driving forces of the rollers 2.1 act upon a radius Rwhich is far greater than the radius r on which the
frictional forces of the rollers 2.2 are acting. If the
rollers 2.2 drive the ball 1, the roller~ 2.1 will, for
the same reason, be unable to hinder this movement. In
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that case, the goods 3 move in a direction perpendicular
to the plane of the drawing.
Figure 5 is a schematic plan view, showing how a displace-
ment at an angle of 45 degrees can be effected by driving
both pairs of rollers 2.1 and 2.2 with the same velocity.
In principle, the goods can be moved in any desired
direction by driving the pairs of rollers with different
velocities and in different directions.
Figure 6 shows how a four-point support can be brought
about by installing cones on two parallel shafts 2.5. In
this example, the cones 2.3 are the driving rollers and
the cones 2.4 have been mounted on the shafts so as to be
freely rotatable.
Figure 7 again relates to part D of Figure 1 and is a
sectional side view, showing how the ball rests on three
rollers (2.1, 2.2, 2.3) which can be driven independently
of each other. Figure 7 also shows how the material to be
displaced can be moved in an arbitrary direction with an
arbitrary velocity V. Vl, V2 and V3 are the peripheral
20 velocities of rollers 2.1, 2.2 and 2.3, respectively.
These rollers do not drive the ball with absolute exact-
ness; the dashed lines denoted by S1, S2 and S3 represent
the components of V which give rise to slip of the ball
relative to the respective rollers. Thus, for instance,
component Sl accounts for a slip velocity SLl in the
proximity of roller 2.1.
The rollers 2.2 and 2.3 have an increased diameter at the
location of the ball, so that the shafts can intersect.
The points of support A, B and C are therefore still in a
horizontal plane. Figure 8 shows how it is thus possible
with few continuous shafts to drive many balls simultane-
ously and in the same direction. With each ball the
recurrent pattern is triangular.
_ 9 _ l 3 0 7 7 5 6
Figure 9 depicts an embodiment in which the number of
levels in the shafts has been reduced to two with the aid
of cone-shaped rollers. In addition, the recurrent
pattern is rectangular, which presents advantages from an
engineering point of view in the construction of rectangu-
lar structures such as, for instance, the component part D
of Figure 1.
Figure 10 shows an example of a variant of Figure 9, in
which the intersecting driving shaft has been replaced by
a freely rotating supporting ball. As one drive unit has
been omitted it is now only the two cones which have to
furnish the driving force in all directions. The effects
of internal slip must therefore be minimized, which is
achieved by positioning the ball precisely between the
shafts. As the ball has to rotate on a horizontal axis
the horizontal velocity of the ball's surface at the level
of the centre of the ball is always equal to zero. So, at
points A and B there is no horizontal velocity and hence
no slip. (For comparison with Figure 4: r = O).
Figure 11 is a plan view, showing how a rotary motion can
be brought about. In this example the balls 1 have been
divided into four groups such that the balls of one group
drive the goods in one specific direction. The directions
of the several groups may be at right angles to each
other.
Figure 12 is a plan view of an embodiment in which it is
indicated
- how the four rollers 2 can be suspended in such a
fashion that ball l invariably rests uniformly on the
four rollers;
- how the drive of the rollers 2 can be laid out such
that the conveyor system's own height is not affected
adversely by intersectinq shafts.
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The bearings 8 of shafts 9, 10, 11 and 12 are fixed in
position, so that these shafts can only rotate on their
axis. Shafts 11 and 12 are provided with flexible coup-
lings 13 to which the shafts 14 carrying the rollers 2
have been attached. The other ends of shafts 14 rest in a
yoke 15 which can move freely about a shaft 16 in the way
indicated by the circular arrow 30. As soon as a ball 1
is positioned between the rollers 2, the yoke 15 will
assume such a position that the four rollers support the
ball uniformly.
The shafts 9 and 11 are interconnected through a chain 17
and the single sprocket wheels 18. Shaft 9 is driven by
the double sprocket wheel 19 which is connected through
chains 20 to other ball drives of the conveyor system.
Shafts 10 and 12 are not interconnected directly through a
chain, because the shafts 9 and 10 lie in the same plane.
The coupling is effected through a gear wheel transmission
at right angles. A bevel gear wheel 21 is rigidly mounted
on shaft 10 and engages a gear wheel 22 which can freely
0 rotate on shaft 9.
The gear wheel 22 has a double bevel configuration and
also meshes with a gear wheel 23 mounted on an ancillary
shaft. Gear wheel 23 and shaft 12 are interconnected
through a chain 24 and a few sprocket wheels 25. Gear
wheel 23 is driven by means of a gear wheel 26 which is
attached to double sprocket wheels 27. These sprocket
wheels 27 and gear wheel 26 can together rotate freely on
shat 9. The sprocket wheels 26 are coupled to other ball
drive units of the conveyor system through chains 28.
Figure 13 shows in more detail following the line A-A in
Figure 12 how a support may be designed so as to have
sufficient flexibility that in the event of overloading a
ball can come to rest on a support 6 (see also Figure 3).
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Figure 14 shows in detail how a roller may itself be
designed so as to have sufficient flexibility that in the
event of overloading a ball can come to rest on a support
6.
Figure 15 shows in detail how a coneshaped roller may
itself be designed so as to have sufficient flexibility
that in the event of overloading a ball can come to rest
on a support 6.
