A METHOD AND APPARATUS FOR CHANGING THE DIRECTION
OF MOTION OF A PALLET MOVING ON WHEELS AT THE
END OF A PASSENGER TRANSPORT CONVEYOR
The present invention relates to a method and to an apparatus for changing the
direction of motion of a pallet at the end of a transport conveyor or equivalent.
Like escalators, transport conveyors are transport devices designed to move
people or goods. They differ from escalators e.g. in that they are often operated
in a substantially horizontal position or in a position somewhat inclined relative to
their direction of motion, typically e.g. by 1-15°, so that successive steps, i.e.
pallets form a substantially even and linear track instead of stair-like steps as in
the case of escalators, instead of successive steps, transport conveyors may
also have a continuous belt, in which case the transport conveyor resembles a
belt conveyor. Transport conveyors are also called moving walkways and
autowalks.
In prior-art transport conveyors, the structure is embedded in the ground or in
the floor of the building. In this case, a pit about one meter deep and several
meters long is provided at either end of the transport conveyor for the drive
machinery of the transport conveyor structure and for the mechanism turning the
pallets. Correspondingly, the depth of the recess needed in the middle part of
the transport conveyor is about half a meter. A drawback with this type of
transport conveyor constructions is that they require heavy and fixed structures
in the floor of the surrounding space and these have to be taken into account
already when the buildings are being designed. A further drawback is that
transferring fixed structures like this from one place to another according to
changing traffic needs is completely impossible.
In prior-art solutions, the pallet track typically consists of pallets that are about
15...40 cm long, corresponding to the steps of escalators. The pallets are
chained together usually by means of a chain or e.g. a cogged belt, and the
whole chain is driven around by a machine and a chain sprocket so that the

upper pallets in the chain move on rollers supported by a special race
track. At the end of the pallet track, at the end of the race track, the pallets turn
upside down around a wheel of a large diameter and return back to the
beginning of the race track by the lower side of the said track. At the beginning
of the track, the pallets again turn around to their normal traveling position and
move further on the upper side of the track towards the end of the race track.
One of the problems with a prior-art solution like this is the turning of the pallet at
the ends, because the height of the turning space has to be at least equal to the
length of the pallet. In practice, however, the height is about 1.5...2 times the
length of the pallet because othenwise the operation will not be smooth enough.
In British patent specification no. GB2299316, Fig. 1/3 presents a structure of
the above-described type as an example of prior art. In addition, this patent
specification discloses a transport conveyor construction wherein the pallets are
guided by fixed tracks at their turning points while being continuously held in a
horizontal position. Thus, the pallet is not turned upside down at the turning
point. Actual control is effected by means of a curved track by the leading
wheels in the direction of motion of the pallet while the trailing wheels are
substantially free. However, this solution disclosed by the GB patent
specification involves the problem that the track has so-called dead centers at its
end points where the position of the pallet is not completely exactly defined. As
a consequence, the pallet may get jammed at the dead center, causing the
entire apparatus to stop as a result of the operation disturbance and may even
be damaged. The risk of jamming is increased by the running clearances, non-
ideal track properties and wear of the mechanism.
The object of the present invention is to overcome the above-mentioned
drawbacks and to create a method and an apparatus for changing the direction
of motion at the end of a transport conveyor or equivalent that is simple in
mechanical construction and reliable in operation. A further object of the
invention is to create a transport conveyor structure of a low construction that
can be mounted directly on a base, e.g. on a floor.
Accordingly, the present invention provides a metliod for changing the
direction of motion of a pallet moving on wheels at the end of a transport
conveyor or equivalent, in which transport conveyor the pallets moving in the
traveling direction move at a different level than the pallets moving in the return
direction, and in which method the direction of motion of the pallet is changed
keeping the pallet in substantially the same attitude throughout the direction-
changing phase in such manner that during direction change the trailing end of
the pallet in the direction of travel is guided by positive control from the level of
the traveling direction to the other level, characterized in that the trailing end of
the pallet as seen in the direction of motion is guided by means of a supporting
element, said supporting element being rotated by means of the pallet
immediately following the one whose direction of motion is being changed, the
drive sprocket, around which the transmission means runs, and the supporting
element being positioned at a distance from each other in the direction of motion
of the pallets.
The present invention also provides an apparatus for changing the direction of
motion of a pallet moving on wheels at the end of a transport conveyor or
equivalent, in which transport conveyor the pallets are coupled to a power
transmission means moving the pallets, such as a cogged belt or a chain, in
such manner that the pallets moving in the direction of travel have been
arranged to move on a different level than the pallets moving in the return
direction, and in which apparatus the direction of motion of the pallet is changed
keeping the pallet in substantially the same attitude throughout the direction-
changing phase, said apparatus comprising a supporting element arranged to
guide during direction change the trailing end of the pallet as seen in the
direction of travel by positive control from the level of the traveling direction to
the other level, characterized in that the supporting element has been arranged
to be rotated by means of the pallet immediately following the one whose
direction of motion is being changed, the drive sprocket, around which the
transmission means runs, and the supporting element being positioned at a
distance fromeach other in the direction of motion of the pallets.
Preferably, during direction cliange the trailing end of the pallet as seen in the
direction of travel is guided by positive control by means of the supporting
element both from the upper level to the lower level and from the lower level to
the upper level. During direction change the supporting element is rotated by
means of the pallet immediately following the one whose direction of motion is
being changed. During direction change the supporting element is rotated by
means of those wheels of the pallet immediately following the one whose
direction of motion is being changed that come foremost in the direction of travel
of the pallet.
Preferably, the supporting element is an idler wheel freely rotating on its axle
and having in its surface a number of indentations corresponding to the wheels
of the pallet. The supporting element is preferably placed at the end of the track
in such a way that the supporting element can be positively rotated by means of
the wheels of the pallet. The supporting element is placed at the end of the track
in such a way that the supporting element can be positively rotated by means of
the wheels of the pallet immediately following the one whose direction of motion
is being changed.
The method and apparatus of the invention, in short the solution of the
invention, has the advantage that its low construction height allows the transport
conveyor structure to be mounted directly on the base. At its lowest, the total
height of the transport conveyor structure is only slightly greater than the height
of two pallets, because the returning pallets must be provided a space to move
under the pallets above. The base may be e.g. an asphalt or concrete surface
either outside or inside a building. The structure does not require any pit or
corresponding space specifically made for it at all, so the solution of the
invention is advantageous in respect of costs and flexible in regard of disposition
in a desired place. Moreover, if necessary, the transport conveyor structure of
the invention can be moved to another place with minor variations and at a low
cost. A further advantage is that the solution of the invention makes it possible to
achieve a light construction such that the floor under the transport conveyor
forms the final reinforcement of the structure.
Yet another advantage is that, due to the solution of the invention, the pallet
will not be jammed at any point during the turning movement, so the structure
works reliably and no operation disturbances due to jamming occur. An
additional advantage is that, during the direction-changing phase, the pallet is
always moved from one level to the other by the trailing wheels relative to the
current direction of motion, i.e. alternately by "front wheels" and by "rear
wheels". This together with the fact that both the pallet and the track have a
mirror image-like structure in the longitudinal direction of the track makes it
possible to achieve a simple construction that allows the pallets to be driven
equally well in both clockwise and anti-clockwise directions. Moving the pallets
by the wheels also provides the advantage that, during the direction-changing
phase, the paths of motion of the pallet are accurate and the operation is quiet
due to a continuous hold. In addition, no extra clatter occurs during the direction-
changing phase because an idler moving the pallets is contact with pallet
bearing wheels provided with a soft surface layer.
In the following, the invention will be described in detail with reference to an
embodiment example and the ccompanying drawings, wherein:
Fig. 1 presents a side view of the exit end of the transport conveyor
structure of the invention.
Fig. 2 presents a sectional side view of the exit end of the transport
conveyor structure of the invention at one stage.
Fig. 3 presents a sectional side view of the exit end of the transport
conveyor structure of the invention at another stage, and
Fig. 4 presents a top view of the exit end of the transport conveyor
structure of the invention.
The transport conveyor structure 13 of the invention comprises a frame structure
14, whose function is to hold the equipment together and transmit the forces to
the base under it. Inside the frame structure is a pallet track, on the upper
surface of which the passengers stand. In addition, the transport conveyor
structure comprises at least a pallet track drive machine including a drive
sprocket 3 and a cogged belt 2, as well as handrails and their drive machine.

The pallet track consists of separate pallets 1 provided with wheels, with front
wheels 5a and 5b located at the front corners of the pallet relative to the normal
direction of transport of the transport conveyor and rear wheels 6a and 6b
located at the rear corners of the pallet. Front wheel 5a is located at a front
corner at a position removed outward by a certain distance relative to the
corresponding rear wheel 6a on the same side of the pallet. Similarly, the rear
wheel 6b on the other side of the pallet is located at a rear corner at a position
removed outward by a certain distance relative to the corresponding front wheel
5b on the same side of the pallet. This certain distance is in both cases of
substantially equal length and at the same time such that it allows rear wheel 6a
to fall onto the return track and likewise front wheel 5b to rise onto the upper
track 7 at the other end of the transport conveyor. Before descending onto the
return track, the pallet is supported through some distance by at least three
wheels 5a, 6a and 6b.
Moreover, each side edge of the pallets 1 is provided with a fastening element 4
placed at about the middle part of the pallet relative to its direction of motion for
fastening the pallet by its side edge to the cogged belt 2. The pallet 1 is fastened
to the cogged belt 2 in such a way that the fastening element 4 allows the pallet
to remain oriented in the same direction, i.e. with the grooved supporting surface
facing substantially upwards throughout the direction-changing phase.
The pallets 1 carrying passengers, driven by the cogged belt 2 and supported by
their wheels 5 and 6, move along the upper tracks 7, whereas the pallets
moving in the return direction, supported by the same wheels, move along a
race track in the lower part of the frame structure 14. At the end of the transport
conveyor, the fonward edge of the pallet goes under a so-called foot board 10,
which is usually a comb blade. At about the same point, the normal track 7
narrows on one side of the transport conveyor into a track extension 11, so that
when the rear wheel 6a reaches that point, the normal track 7 provides no
support for it. Therefore, in the region of the extension 11, the rear wheel 6a can
freely move through a passage opening 11 a onto the return track. The track
extension 11 extends as a narrower track and is located on the line of motion of
the outer wheel 5a at the front edge of the pallet, at substantially the same
level with the track 7. Thus, the outer front wheel 5a is supported on the
extension 11 to prevent tilting of the front end of the pallet at the beginning of the
direction-changing phase. The distance of the rear wheel 6a on the
corresponding side of the pallet from the side edge of the pallet has been so
chosen that it is smaller than the distance of the front wheel 5a so that the rear
wheel 6a does not extend onto the track extension 11. Consequently, the
extension 11 does not prevent the rear part of the pallet from descending
through the passage opening 11 a to the level of the race track in the frame
structure 14 during the direction-changing phase.
The transport conveyor may have a corresponding track structure at the entry
end of the pallet track as well, in which case the structure is a longitudinal mirror
image of the exit end structure described above. At the entry end, rear wheel 6b
is supported on a corresponding extension and front wheel 5b can rise to its
upper position by the front end of the beginning of the track, where a suitable
opening is provided for the front wheel 5b located closer to the inner edge of the
pallet. As the entry end structure is substantially identical to the structure of the
exit end, the entry end is not shown separately in the drawings.
Placed at the fonward end of the each track 7 is an idler 8 functioning as a
supporting element supporting the rear end of the pallet 1. The idler forms an
extension of the track and is mounted on an axle so as to be freely rotatable.
The idler 8 is of an indented wheel design such that the idler 8 has e.g. four
indentations 12 having the shape of a circular arc corresponding to the wheels
5a, 5b and 6a, 6b of the pallet 1, which indentations first receive the front wheels
5a, 5b and then the rear wheels 6a, 6b of the pallet as it passes over the idler 8
at the exit or second end of the transport conveyor so that the idler 8 is always in
engagement with wheels of at least three pallets. At the same time, the idler 8
moves the rear end of the pallet 1 downwards past a possible dead center when
the direction of motion of the pallet is being changed. The idler 8 receives its
drive from the next pallet, whose front wheel 5a, 5b causes the idler to go on
rotating. The placement and structure of the idler 8, the distances between
successive indentations as well as the width of the idler have been so chosen
that both the front wheel 5a, 5b and the rear wheel 6a, 6b of the pallet 1 are
received In turn In the idler Indentations 12, whose radius of curvature Is at least
equal to but preferably somewhat larger than the radius of the wheels 5a, 5b
and 6a, 6b of the pallet. Since the idler 8 rotated under positive control supports
the rear end of the pallet at the exit end of the transport conveyor and controls
Its movement during the change of direction, the position of the pallet is
accurately controlled throughout the direction-changing phase, so the motion of
the pallet can not get jammed at any point during the change of direction.
The dimensions of a construction comprising an idler 8 with four indentations
are bound by the following equation:
L = 1/2 *(p-''/2*r), where
L = distance of the rotational center of the idler 8 from the rotational center of
the drive sprocket 3; it is also the distance of the hub of the wheels 5 and
6 from the fastening element 4 of the pallet 1
p= distance between the fastening elements 4 of successive pallets,
preferably as an even number of cogs or chain elements
r = radius of the sprocket.
After the track extension 11 in the direction of motion of the pallet track there is a
passage opening lib, whose position and length have been so chosen that the
pallet fastening element 4 can move through the passage opening 4 from the
upper position to the lower position during direction change. Similarly, on the
other side of the transport conveyor, directly opposite to the track extension 11
and passage opening lib, there is a passage opening 11c preferably extending
to the first end of a rest bar 9 located at a distance from the idler 8 at the end of
the track. During the change of direction of the pallet, rear wheel 6b and the
second fastening element 4 move through passage opening 11c from the upper
level to the lower level.
The length of the bearing surface of the rest bars 9 located after the passage
openings lib and 11c in the direction of motion of the pallet track has been so
chosen that the pallet's front wheels 5a, 5b supported by the rest bar 9 can
move around the rounded front end of the rest bar 9 from the upper position of
the pallet to the lower position of the pallet to the level of the inner surface of the
bottom of the frame structure 14. The drive sprocket 3, which in Fig. 2, 3 and 4
is only represented by the shaft of the drive sprocket, is placed between the
idlers 8 and the rest bars 9 as seen in the direction of motion of the pallets 1.
The endless cogged belt 2 runs around the castellated drive sprocket 3 of the
drive machine at each end of the track. The drive sprocket 3 is driven by the
drive machine, which is not presented in the figures. The pallets 1 attached to
the cogged belt 2 move together with the cogged belt, forming an endless track
for transporting passengers from the entry end of the transport conveyor to the
exit end of the transport conveyor.
As stated above, the structure of the apparatus at the entry end of the transport
conveyor is identical to the above-described structure of the exit end of the
transport conveyor. At the entry end, the pallet is guided from its lower position
to the upper position by positive control as described above. In this case, the
pallet's front wheels 5a, 5b, which in this direction of motion are the trailing
wheels, are supported by the idlers 8, and the front end of each pallet is raised
under positive control from the lower level to the transport level, in other words,
the pallet is raised in a substantially horizontal plane to the track level 7. Due to
the positive operation, the apparatus works without any jamming problems in
both directions of motion.
By the method of the invention, the direction of motion of the pallet 1 is changed
while keeping the pallet in substantially the same attitude throughout the
direction-changing phase in such manner that during direction change the
trailing end of the pallet 1 relative to the current direction of motion is guided by
positive control from the level of the current direction of motion to the other level.
In more accurate terms, during direction change the trailing end of the pallet 1
as seen in the direction of motion is guided by positive control by means of the
idler 8 from the level of the current direction of motion to the other level. The
control of the motion is facilitated by the fact that during direction change the
9
idler 8 is positively rotated by those wheels 5a, 5b or 6a, 6b of the pallet
immediately following the one whose direction of motion is being changed that
come foremost in the current direction of motion.
in the above, the same attitude of the pallet 1 means that pallet is never turned
upside down, but the pallet is moved from one level to the other in a
substantially horizontal position, although a slight inclination in the forward or
backward direction relative to the direction of motion is possible.
It is obvious to the person sl