Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 This invention relates to line shaf-t live roller
conveyors and more particularly to a locating device for axially
locating the drive spools on the drive shaft thereof.
Line shaft live roller conveyors have a number of
rollers arranged to carry boxes or other individual articles
along a pass line. Each roller is individually driven by an
elastomeric drive belt extending around a spool on a common line
or drive shaft located beneath the rollers. In order to provide
for accumulation of the articles on the conveyor, it is necessary
that one or more of the rollers be able to stop while the others
keep rotating. This independent roller operation is provided
for by having the individual driving spools which are spaced
along the drive shaft only lightly frictionally engaged by the
drive shaft so that they may slip if necessary when the roller
driven by that spool is stopped by an article sitting on it.
As is well known in the art, this type of line shaft
i live roller conveyor produces a phenGmenon whereby the spools
move axially downstream along the drive shaft when no load is
applied to the driven rollers and then shift upstream to a
position beneath the driven rollers when load is applied and
this phenomenon is known as "axial shift". While this phenomenon
is not completely understood, as discussed in Canadian Patent
930,686 to Fleischauer et al. which issued July 24, 1973, it
has been thought to be as a result of the tensioning imbalance
on the drive belt and the fact that the spools are able to cock
slightly due to the play between them and the drive shaft. In
Canadian Patent 930,686, this phenomenon of "axiàl shift" was
presented as an advantage in that it has a self-tensioning
effect on the drive belt as the load is applied. However, in
practice, it has been found to be unacceptable in that it
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1 ~ventually results in the elastomeric belts being stretched to
the point where they lose their power and have to be replaced.
This problem is aggrevated by the fact that the spools shift
closer to their respective roller when the load is applied,
rather than further away. This has lead to the use of cylindri-
cal plastic spacers located on the drive shaft between the spools
to prevent "axial shift".
However, it has been found that these spacers have
several problems or disadvantages. The length of the spacers
must correspond to the desired distance between the rollers and
if it is necessary to change the roller spacing, the spacers
and spools must all be taken off of the drive shaft and the
spacers replaced. Similarly, this~;must also be done if there is
a failure of one of the spacers requiring that it be replaced.
More importantly, it has been found that the independent operation
of the individual rollers may be lost, at least to some extent,
by forces being transmitted through the spacers between adjacent
spools. When conveyor accumulation occurs and a box is stopped
on a roller, the phenomenon of "axiàl shift" mentioned above
tends to move the spool driving that roller in a downstream
direction as it comes to a stop. However, when cylindrical
spacers are located on the drive shaft between each of the spools,
this jams all of the spacers and spools in that section of the
conveyor together which tends to prevent this and other adjacent
rollers upon which the box may be sitting from stopping. In
other words, the line pressure on the box is increased because
the force being exerted on the box is greater than that
originating only from the rollers upon which it is sitting. This
detrimentally effects the operation of the means used to stop the
box and therefore, the whole accumulation operation of the
conveyor.
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1 Accordingly, it is an object of the present invention
to at least partially overcome these disadvantages by providing
a locating device which may be manually snapped onto the drive
shaft downstream of a spool to axially locate that spool in a
desired position along the drive shaft without making contact
with any other spool, and which may be easily relocated to shift
the axial position of the spool on the drive shaft.
To this end, in one of its aspects, the invention
provides a device for axially locating a spool on a cylindrical
10 drive shaft in a line shaft live roller conveyor having a
plurality of said rollers which form a pass line thereon to
carry objects along the conveyor, drive shaft extending generally
transversely to said rollers, said drive shaft carrying a plur-
ality of said spools, each spool being rotated or not rotated by
` said shaft depending upon the degree of frictional engagement
therebetween, a plurality of endless elastomeric drive belts,
: each having a round cross section and extending around one of
said spools and through a circumferential groove around a
respective one of said rollers, said locating device having a
C-shaped body which forms a mouth, the body being formed of
resilient material and extending around more than 180 to
provide the mouth with a height significantly less than the out-
side diameter of said drive shaft and being of a size whereby it
may be manually snapped transversely onto said drive shaft to a
position where it grips the drive shaft with sufficient force
to prevent it being axially displaced or accidently dislodged
from the drive shaft by the normal operating force of a spool,
although allowing it to be manually relocated along the drive
shaft, said locating device normally being positioned on the
drive shaft adjacent said spool to locate the spool against
1 downstream shifting along the drive shaft.
Further objects and advantages of the invention will
appear from the following description taken together with the
accompanying drawings in which:
Figure 1 is a perspective view of a section of line
shaft live roller conveyor ulitizing locating devices according
to a preferred embodiment of the invention;
Figure 2 is an enlarged elevation view showing one of
the locating devices seen in Figure 1 locating a spool on the
drive shaft; and
Figure 3 is a perspective view of the locating device
seen in Figures 1 and 2.
Reference is first made to Figure 1 which shows a
portion of a line shaft live roller conveyor 10 having a number
of rollers 12 supported by two side frame members 14, 16. The
upper surfaces of the rollers 12 form a conveyor pass line
along which boxes or other articles are transported. A line
or drive shaft 18, driven by a power source~not shown) is located
beneath the rollers 12 and extends transversely to them. The
~ drive shaft 18 carries a number of spools 22, and an elastomeric
drive belt 24 having a uniform round cross section extends from
each spool 22 through a groove 26 in a respective one of the
rollers 12.
It is necessary for the succ~ssful operation of this -
type of conveyor that provision be made for the accumulation
of boxes on it, and in order to facilitate accumulation, it is
desirahle that only the particular rollers under a box stop
rotating when that box is stopped on the conveyor by other means
(not shown). It is well known in the art to provide for this
by having a relatively loose fit between the spools 22 and the
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line shaft or drive shaft 18~ Thus, when a particular roller 12
is stopped rotating by a box being s-topped on it, the spool 22
from which it is driven slips on the drive shaft 18 to provide
this individual or independent roller drive function. However,
as may be seen, the location and alignment of the drive shaft
18 requires that the rotational axes of the spools 22 be at an
angle of substantially 90 to that of the rollers 12. This
factor, combined with the necessarily loose frictional fit of
the spools 22 on the drive shaft 18, results in the undesirable
phenomenon mentioned above of axial shifting of the spools 22 on
the line shaft 18. In a no-load or idling state, each rotating
spool 22 tends to slip on the drive shaft to position itself
slightly downstream from the roller 12 it is driving. When a
load is applied to the roller, the driving spool would be drawn
upstream to a position more directly beneath the roller.
According to the present invention, this phenomenon of axial
shifting is prevented by locating devices 28 which are snapped
onto the drive shaft adjacent the downstream side 30 of each
spool 22.
In this embodiment, the locating device has a body 32
with a uniform C-shaped cross section and mouth 34. The shape
of the inner surface 36 is slightly off~cylindrical when the
locating device is in the unstressed state, whereby when it is
stressed to resiliently engage the cylindrical drive shaft 18,
it assumes a cylindrical shape to grip the outer surface of the
drive shaft 18. While the inner surface 36 is smooth in the
embodiment shown, it may be textured or otherwise designed to
improve its grip on the outer surface of the drive shaft 18
during use. The C-shaped body 32 extends around about 240 to
provide the mouth 34 with a height in the unstressed state which
1 is significantly less than the diameter of the drive shaft 18.
~s this dimension, combined with the resiliency of the material,
determines the amount of force required to install and remove
the locating device, it may be varied depending upon the
application. However, it will be apparent that the C-shaped
body must extend around more than 180 in order to be securely
retained in the installed position. The body 32 also has a
smooth outer surface 38 and smooth side walls 40, 42 to minimize
frictional forces arising on contact with a spool. While this
embodiment of the invention is formed of DELRIN (a Trade Mark
of DuPont of Canada Limited for an acetate product containing
an anti-static agent to avoid dirt accumulation), it may be
formed of any suitable material providing the necessary strength
and resiliency characteristics.
In use, the locating device 28 is snapped onto the
drive shaft 18 by manually forcing it transversely against the
drive shaft 18 until the mouth 34 of the C-shaped body 32
expands sufficiently to accommodate the drive shaft. When it
snaps over the drive shaft, the resiliency of the material
causes the inner surface 36 to securely grip the drive shaft in
a fixed position. A locating device 28 is positioned adjacent
each spool 22 on the downstream side to locate the spool against
downstream axial shifting of the spool when the load is removed
from the rollers. The width of the body, together with its
resiliency is selected to ensure that the locating device grips
the drive shaft 18 with sufficient strength to prevent it being
axially displaced by the operating force of the spool, while at
the same time allowing it to be manually relocated along the
drive shaft.
Thus, while each locating device is in contact with a
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spool on its upstream side, there is no contact with any other
spool which necessarily avoids the transmission of forces
between adjacent spools by the locating devices. Furthermore,
while the locating devices 28 are fixed to the drive shaft 18
and rotate with it and therefore will each have some effect on
the adjacent spool 22 due to front frictional contact between
them, this effect will be the same for each spool and therefore
may be taken into consideration in the design of the accumulation
means for the conveyor 10. If the conveyor is reversible, then
it will be apparent that it is necessary to position locating
devices 28 on both sides of each spool 22 to prevent axial
shifting in either direction.
The locating devices 28 according to the invention may
also advantageously be used with the new so-called "self
centering" type of line shaft live roller conveyor drive. Even
if the locating devices are not re~uired to prevent intermittent
! axial shifting of the spools 22, they may be used to slightly
shift each spool 22 away from a position directly beneath the
driven roller 12 to increase tension in the drive belt 24 to a
desired value. It will be appreciated that the fact that each
locating device 28 may be quickly and easily relocated on the
drive shaft 18 by manually sliding it along makes this very
useful to compensate for stretching of the elastomeric drive
belts 24 which ultimately occurs after long periods of use.
Although the disclosure describes and illustrates a
preferred embodiment of the invention, it is to be understood
that the invention is not restricted to this particular embodi-
ment. Many variations and modifications will now occur to those
skilled in the art. In particular, it will be apparent that
locating devices having other shapes and sizes and formed of
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1 other materials may be used For a definition of the invention,
reference is made to the appended claims.
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