U.S. patent number 3,724,840 [Application Number 05/138,549] was granted by the patent office on 1973-04-03 for stacking apparatus for sheet articles fed in overlapping formation on a continuously moving conveyor towards a stacking station.
This patent grant is currently assigned to Windmoller & Holscher. Invention is credited to Gustav Kuckhermann.
United States Patent |
3,724,840 |
Kuckhermann |
April 3, 1973 |
STACKING APPARATUS FOR SHEET ARTICLES FED IN OVERLAPPING FORMATION
ON A CONTINUOUSLY MOVING CONVEYOR TOWARDS A STACKING STATION
Abstract
A stacking apparatus for sheet articles fed in overlapping
formation on a continuously moving conveyor towards a stacking
station, wherein the lowermost article of each intended stack is
temporarily held stationary on the conveyor so that succeeding
articles destined for the same stack bank up and their degree of
overlap is increased before the lowermost article is released
again. A braking device is progressively applied to the succeeding
articles in an upstream direction at a speed so that their leading
edges become held at uniform spacings from one another and is
released from all the articles when the lowermost article is also
released.
Inventors: |
Kuckhermann; Gustav (Lengerich
of Westphalia, DT) |
Assignee: |
Windmoller & Holscher
(Westphalia, DT)
|
Family
ID: |
22482529 |
Appl.
No.: |
05/138,549 |
Filed: |
April 29, 1971 |
Current U.S.
Class: |
271/182;
271/270 |
Current CPC
Class: |
B65H
29/6654 (20130101); B65H 33/12 (20130101); B65H
2511/22 (20130101) |
Current International
Class: |
B65H
29/66 (20060101); B65h 029/66 () |
Field of
Search: |
;271/46,DIG.8,75,76,77,7,47 ;198/35 ;93/93DP |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Blunk; Evon C.
Assistant Examiner: Stoner, Jr.; Bruce H.
Claims
I claim:
1. A stacking apparatus for sheet articles, comprising a
continuously moving conveyor for feeding said sheet articles in
overlapping scale formation, means for holding temporarily
stationary the lowermost article of a stack to be formed at a
stacking station to space the lowermost article from preceding
articles of the overlapping formation and to cause succeeding
articles of the overlapping formation to be restrained, braking
means adapted to be applied to the leading edges of said succeeding
articles during their restraint, the position of braking effect
progressing in a direction opposite to the feeding direction of the
articles and at a speed so that the relationship between the
conveyor speed and the speed at which the braking effect progresses
is constant, the braking means being adapted to be lifted from said
succeeding articles when said lowermost article is released
again.
2. Apparatus according to claim 1, wherein the conveyor comprises a
plurality of parallel spaced belts, slide rails disposed flush with
the conveying runs of the belts extend along the spaces
therebetween, and the braking means comprise spaced strips which
are disposed above the side rails, are held stationary by at least
one end and are movable from above towards the said succeeding
articles.
3. Apparatus according to claim 2, wherein the strips are flexible
bands fixed by their downstream ends to a clamping bar which is
reciprocatable towards the said lowermost article to hold the
leading end thereof stationary, the upstream ends of the bands
being attached to a point spaced above the conveyor, and wherein at
least one pressure roll which is movable in the upstream direction
during restraint of the succeeding articles is provided for
pressing on the bands from above against the succeeding articles
before being retracted in the downstream direction after the said
lowermost article has been released.
4. Apparatus according to claim 3, wherein the pressure roll is
retracted whilst it is lifted so as not to press the bands against
the successive articles.
5. Apparatus according to claim 2, wherein the strips are upwardly
concave resilient metal bands fixed by their downstream ends to a
clamping bar which is reciprocatable towards the said lowermost
article to hold the leading end thereof stationary, and wherein the
upstream ends of the bands are movable towards the said succeeding
articles during the restraint thereof and away therefrom after the
said lowermost article has been released.
6. Apparatus according to claim 5, wherein the bands are of spring
steel.
Description
The invention relates to a stacking apparatus for sheet articles
fed in overlapping formation on a continuously moving conveyor
towards a stacking station, wherein the lowermost article of each
intended stack is temporarily held stationary on the conveyor so
that succeeding articles destined for the same stack bank up and
their degree of overlap is increased before the lowermost article
is released again. The sheet articles with which the invention is
primarily concerned are flattened paper or plastics tube sections
or flattened sacks or bags made from such tube sections.
Stacking apparatus of the kind with which the invention is
concerned is described for example in U.S. Pat. No. 2,919,789. At
predetermined time intervals, an article in the overlapping
formation is temporarily held stationary on the conveyor, which
continues to move. The succeeding articles therefore bank up, being
restrained by the stationary article, whilst the preceding articles
continue to move towards the stacking station and become separated
from the stationary article to be stacked and transported away
before the temporarily held article and the articles succeeding the
same arrive at the stacking station.
In practice, it has been found that the separated preceding
articles, which may be stacked by being flung into a stacking box
or onto a stacking belt, do not reliably form stacks in which the
edges of all the articles are accurately aligned, especially if the
articles are made of very flexible materials such as thin paper or
plastics film. We have found that the cause for this is uneven
overlapping of the articles caused by uneven banking up on the
temporarily held article. It has been observed that, although the
articles succeeding the held article start to bank up evenly to
result in equal degrees of overlap, uneven spacings between the
leading edges of the articles occur as the articles are continued
to be pushed together. The reason is probably that the frictional
forces between the faces of the initially only slightly overlapping
articles are smaller than the frictional forces between the
conveyor and the relatively large faces of the articles in contact
therewith. As the articles are pushed together, the contact faces
between the articles increase, with a resultant increase in the
frictional forces, whilst the frictional forces between the
articles and the conveyor are reduced because the area of contact
between the articles and the conveyor becomes progressively less.
To begin with, therefore, the conveyor is instrumental in uniformly
pushing the articles over one another and thereby producing a
uniform increase in the degree of overlap. However, as soon as the
frictional forces between the partially superposed articles are
equal to the frictional forces existing between the articles and
the conveyor, further banking up of the articles will be dependent
on local frictional conditions as determined by any haphazard
differences that may occur in the surface properties of the
individual articles. The row of articles succeeding the temporarily
held article will therefore continue to bank up only at those
positions where the frictional force between two adjacent articles
is less than elsewhere. This gives rise to considerable differences
in the spacings between the leading edges of the articles and these
differences are retained right along the production line until they
eventually detrimentally influence the accurate superpositioning of
the articles at the stacking station.
The invention aims to avoid non-uniform overlapping of the articles
in the banked-up row and thereby facilitate stacking of the
articles at the downstream stacking station. For this purpose, the
invention proposes the use of a braking device which is
progressively applied to the succeeding articles in an upstream
direction at a speed so that their leading edges become held at
uniform spacings from one another and which is released from all
the articles when the temporarily held article is also
released.
More particularly, in a stacking apparatus for sheet articles fed
in overlapping scale formation on a continuously moving conveyor,
in which the lowermost article of each stack to be formed at a
stacking station is temporarily held stationary to space it from
preceding articles of the overlapping formation and to cause
succeeding articles of the overlapping formation to be restrained,
the invention makes provision of braking means which are adapted to
be progressively applied to the leading edges of said succeeding
articles during their restraint in a direction opposite to the
feeding direction of the articles and at a speed so that the said
leading edges are held at uniform spacings from one another, the
braking means being adapted to be lifted from said succeeding
articles when said lowermost article is released again.
The braking means lying on the succeeding articles prevent the
articles therebeneath from being pushed further together. By
appropriately selecting the speed at which the braking means are
progressively applied, with due regard to the speed of the
continuously moving conveyor, it is now simple to ensure that the
succeeding articles are held before the aforementioned frictional
forces become equal, i.e. before the degree of overlap becomes
uncontrollable. The most favorable relationship between the
conveyor speed and the speed at which the braking means are
progressively applied to the articles is found by experimentally
altering one or both of the speeds for a particular size and
material of the articles.
The lowermost article for each stack can be temporarily held
stationary on the conveyor by means of a reciprocatable clamping
bar which is placed over the leading edge of the article and by
suckers which simultaneously engage the trailing edge of the
article, the conveyor in this case comprising a plurality of
parallel spaced belts between which the suckers can reach the
trailing edge. Slide rails disposed flush with the conveying runs
of the belts may also extend along the spaces between the belts,
the braking means comprising spaced strips which are disposed above
the slide rails, are held stationary by at least one end and are
movable from above towards the said succeeding articles. Such an
arrangement has the advantage that the pressure of the brake strips
does not press the articles to the conveyor belts simultaneously --
which would only have the result that the driving force of the
conveyor belts that needs to be overcome when stopping the articles
is unnecessarily increased and would cause the articles near the
conveyor belt to be advanced and the top articles to be braked.
The brake strips may be flexible bands fixed by their downstream
ends to the clamping bar, the upstream ends being attached to a
point spaced above the conveyor, and at least one pressure roll
which is movable in the upstream direction during restraint of the
succeeding articles may be provided for pressing on the bands from
above against the succeeding articles before being retracted in the
downstream direction after the said lowermost article has been
released.
In another form of the invention, the brake strips are upwardly
concave resilient metal bands, preferably of spring steel, fixed by
their downstream ends to the clamping bar, the upstream ends being
movable towards the succeeding articles during the restraint
thereof and away therefrom after the lowermost article has been
released.
Two examples of the invention are illustrated in the accompanying
diagrammatic drawings, wherein:
FIG. 1 is a side elevation of part of a stacking apparatus;
FIG. 2 is a plan view of the apparatus taken on the line II--II in
FIG. 1;
FIG. 3 is a side elevation of part of a modified stacking
apparatus, and
FIG. 4 is a plan view taken on the line IV--IV in FIG. 3.
Referring to all the drawings, sheet articles W, for example
flattened paper or plastics tube sections for making into sacks or
bags are discharged from a tube-making machine (not shown) and
deposited on a conveyor 1 which feeds the tube sections in the
direction of the arrow a at a slower speed than the speed at which
they are discharged from the machine so that the articles on the
conveyor are fed in an overlapping scale formation with a uniform
spacing x between the leading edges of adjacent articles. As
evident from FIGS. 2 and 4, the conveyor 1 consists of a plurality
of parallel spaced belts which pass over rollers 2. At the
downstream end of the conveyor 1 there is a clamping bar 3 provided
with clamping shoes 4 located over the gaps between adjacent belts
of the conveyor 1. Tapered slide rails 5 extend along the gaps
between the belts and are flush with their conveyor runs. The
clamping bar 3 is reciprocatable in the directions of the arrows b
in the same sequence as that in which the stacks are to be formed
so that the shoes 4 are lightly applied to the rails 5. Upstream of
the clamping bar and beneath the conveying runs of the conveyor
belts reciprocatable suckers 6 are located to both sides of the
rails 5 at a spacing from the clamping shoes 4 that is less than
the shortest length of article that might be encountered. The
sequence of reciprocating movement of the suckers 6 is equal but
opposite to that of the clamping bar 3. Downstream of the conveyor
1 a feed belt 7 can be set into operation at the same speed as the
conveyor 1 when the clamping shoes 4 are lifted from the slide
rails 5 and at a higher speed when the clamping shoes are applied
to the slide rails. The feed belt 7 is followed by a stacking
station (not shown) which may comprise any suitable stacking belt
or stacking table.
By simultaneously lowering the clamping bar 3 and raising the
suckers 6 towards the overlapping articles W moving on the conveyor
1, one particular article W1 is engaged and held stationary at its
leading and trailing ends. At the same time, the feeding belt 7 is
accelerated. Accordingly, articles preceding the article W1 become
separated therefrom and are conveyed at an elevated speed to the
stacking station whilst articles succeeding the article W1 bank up
to overlap to a greater extent. The feeding belt 7 is associated
with a vigorously effective pressure roll 8 which engages and pulls
out the article W2 which is still located beneath the article W1 at
the instant the latter is held stationary. Whilst the articles
succeeding the article W1 are being banked up, the spacings between
the trailing edges of adjacent articles (and thus between the
leading edges of adjacent articles) are reduced to the dimension y
indicated in FIGS. 1 and 3. Banking up continues for a time
interval which is sufficient to allow the preceding articles to be
stacked and withdrawn from the stacking station. Thereafter, the
article W1 is released by lifting the clamping bar 3 and
interrupting the suction effect of the suckers 6, the feeding belt
7 being simultaneously slowed down to the same speed as that of the
conveyor 1. The banked-up row of articles is now advanced by the
conveyor 1 and belt 7 for a period which will determine the number
of articles reaching the belt 7 and thus the number of articles
forming each stack. Thereafter, another article is temporarily held
stationary and the abovedescribed procedure is repeated.
To facilitate uniform banking-up of the articles on the conveyor 1
of the apparatus shown in FIGS. 1 and 2, brake bands 9 of flexible
material are provided above the conveyor. These brake bands have
their right-hand ends fixed to the clamping shoes 4 and their
left-hand ends secured to a common supporting bar 12 which, in
turn, is attached to a stationary portion 11 of a frame of the
apparatus by means of springs 10 which hold the brake bands under
tension. The brake bands are disposed over the gaps between
adjacent belts of the conveyor 1 and thus over the slide rails 5,
with which they co-operate. The brake bands 9 pass over guide
rollers 13, 14 carried by a carriage 15 which is reciprocatable in
the direction of the arrows d1 by means of a chain 18 passing over
sprockets 16, 17. The lower guide rollers 14 are reciprocatable in
the direction of the arrows c by means of a piston-cylinder
arrangement 19 so as to press the brake bands against the banked-up
row of articles. The other guide rollers 13 divert the brake bands
obliquely upwardly and horizontally.
In the chain-dotted starting position shown in FIG. 1, the guide
rollers 14 are in their raised condition to support the brake bands
9 at such an elevation from the articles W that the free passage of
the latter therebeneath will not be obstructed. From this starting
position, the guide rollers 14 move downwardly at the same time as
the clamping bar 3 is lowered and they press the brake bands 9 with
resilient pressure against the article W1 which is simultaneously
being engaged and held stationary by the clamping shoes 4 and
suckers 6. Directly thereafter, the carriage 15 is uniformly moved
in an upstream direction so that, under the action of the guide
rollers 14, the brake bands are progressively applied with light
pressure against the articles that are being banked up upstream of
the article W1. The speed of the carriage 15 relatively to the
feeding speed of the conveyor 1 is selected so that the spacings x
between adjacent articles successively held by the brake bands 9
against the thrust of the upstream articles are uniformly reduced
to the dimensions y. Progressive application of the brake bands to
the articles is terminated by raising the guide rollers 14, this
taking place simultaneously with lifting of the clamping bar 3 and
terminating the suction effect from the suckers 6. The article W1
and the succeeding banked-up articles are now released for
transport by the conveyor 1 and belt 7 whilst the carriage 15
returns to its starting position.
In the FIGS. 3 and 4 embodiment of the stacking apparatus,
resilient brake bands 20 are provided which are preferably of
spring steel curved to be upwardly concave. One end of each brake
band 20 is fixed to the lower faces of the clamping shoes 4. Near
the other ends, pressure rollers 21 are provided which are
uniformly reciprocatable in the direction of the arrows d by means
of a piston-cylinder arrangement 22. As in the case of the FIG. 1
embodiment, the brake bands 20 are disposed above the slide rails 5
with which they co-operate.
The brake bands 20 are lowered by the clamping shoes 4 so that
their right-hand end is lightly applied to the article W1 which is
simultaneously held stationary by the clamping shoes 4 and suckers
6. Directly thereafter, the pressure rollers 21 are constantly
lowered from their upper starting position shown in chain-dotted
lines in FIG. 3 and thereby progressively apply the brake bands 20
with a rolling action and slight pressure to the articles W that
are banking up therebeneath. The speed of this rolling motion that
is applied in a direction opposite to the feeding direction of the
articles is governed by the speed at which the rollers 21 are
actuated by the piston-cylinder arrangement 22 and is selected in
relation to the speed of the conveyor 1 so that the spacings x of
the articles successively engaged by the brake bands 20 are
uniformly reduced to the dimension y. The banked-up articles are
released for continued transport by the conveyor 1 and feed belt 7
by simultaneously raising the pressure rolls 21 and clamping bar 3
and discontinuing the suction effect from the suckers 6.
* * * * *