Singulation mechanism

Details Singulation mechanism Singulation mechanism

2001-01-30

2003-06-10

Skaggs, H. Grant (Department: 3653)

Sheet feeding or delivering

Feeding

Separator and conveyor

C271S096000, C271S098000, C271S099000, C271S104000, C271S108000, C271S010030, C271S265020

Reexamination Certificate

active

06575450

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to handling and processing systems for mixed mail and related articles, and more particularly to a singulation mechanism for use in such systems which facilitate the handling of articles having significant variation in size, thickness and weight.
BACKGROUND OF THE INVENTION
Mixed mail received at a post office or other location must be sorted and/or otherwise processed so as to be directable to a desired location. To accomplish this function, random items of incoming mail are typically stacked, either manually or otherwise, for feeding to a first mechanism which singulates the mail so that only a single piece of such mail, which is properly oriented and spaced, is passed on to the sorting or other processing mechanism of a mail handling system.
While many mechanisms currently on the market do an adequate job of singulating certain types of mail, increasing demands are being placed on such systems, both as to the ranges in size, thickness and weight of the mail pieces to be handled and as to the speed at which such systems are to operate, while still maintaining high controllability on the outputted mail pieces, a low jam rate, low damage rate and substantial elimination of doubles passing into the sorting mechanism. For example, a specification for mail pieces to be handled in such a high performance system might include pieces ranging in thickness from 0.007″ to 1.25″, pieces ranging in weight from 0.03 oz to 6.0 lbs., and pieces ranging in size from 3.5×″5.0″ or 4.0×″4.0″ to 15″×15″. These variations in thickness, weight and size must be handled without sacrificing throughput, which may be up to approximately 14,500 mail pieces per hour, although this maximum rate may vary somewhat with the size of the pieces being processed, and preferably with an ability to control this rate. Further while the requirements discussed above are particularly applicable to mail handling systems, they can also arise in handling systems for packages and/or other generally flat articles.
A singulation mechanism designed to meet these specifications is taught in co-pending application Ser. No. 09/411,961, filed Oct. 4, 1999, entitled “Singulation Mechanism” and assigned to the assignee of this application. The subject matter of this co-pending application is incorporated herein by reference. The system of the prior application, which is shown in attached
FIG. 1A
, includes a singulation station
14
which receives a stack of mail or other appropriate flat articles
62
, which articles contact a guide wall
32
on their leading edge side, and feeds such articles, one at a time, to a takeaway mechanism
16
. Singulation station
14
includes a head against which articles
62
are pressed with a controlled pressure by mechanisms not shown in the Figure. The singulation head includes a selectively perforated belt
34
driven by rollers
50
A-
50
E so as to pass in direction
38
over a pair of vacuum chambers V
1
, V
2
, chamber V
1
being under a trailing side of each article
62
, and chamber V
2
being under a leading side of each article. A first sensor FL
1
detects articles as they leave singulation station
14
, and a second sensor FL
2
senses articles as they reach a pinch roller mechanism
52
of takeaway mechanism
16
.
In operation, vacuum chamber V
1
is first operated, as shown in
FIG. 1B
, to pull a trailing side of the article
16
in contact with belt
34
against the portion of belt
34
over the V
1
chamber. Since belt
34
has a very low friction surface, only the portion of the belt over the V
1
chamber engages a leading article
62
of the stack and causes the article to move with belt
34
in direction
38
. The distance between the leading edge of chamber V
1
and sensor FL
1
is such that the leading edge of even the smallest article
62
will reach FL
1
before the trailing edge of the article is no longer over chamber V
1
. When the leading edge of the article is detected by sensor FL
1
, suitable controls are operative to turn off chamber V
1
and to at the same time apply vacuum pressure to chamber V
2
. The turning off of vacuum pressure from chamber V
1
prevents chamber V
1
from feeding the next article in the stack, thus preventing the feeding of doubles, and the energization of chamber V
2
causes belt
34
to engage the trailing portion of the article being fed and to advance this article to takeaway station
16
. There is a slight deceleration of the article as chamber V
1
stops driving it and chamber V
2
is not fully operational. This deceleration, followed by a rapid acceleration as chamber V
2
kicks in, tends to shake loose any double adhering to the article being fed. Again, the distance between the leading end of chamber V
2
and sensor FL
2
/pinch roller
52
is less than the length of the shortest article being fed, this assuring that chamber V
2
can feed all articles
62
to be fed to pinch roller
52
where they are detected by detector FL
2
. When the article reaches roller
52
, its motion in direction
38
can be taken over by takeaway mechanism
16
, and chamber V
2
is therefore turned off as shown in FIG.
1
B.
While the singulation mechanism of
FIGS. 1A and 1B
provides far superior performance in meeting the specifications indicated above than any prior singulation mechanism, in practice, the large variations in size, thickness and weight for the articles being fed has made it difficult to provide sufficient vacuum to feed heavier articles to be fed, for example articles weighing 4-6 pounds, while not having so much vacuum that it bleeds through thinner articles, resulting in doubles being fed. It has therefore been very difficult to select the vacuum pressures for both chambers so as to be able to feed all articles, and in particular all mail items, within the above specification without also causing the feeding of an unacceptably high number of doubles.
A second problem with the device shown in
FIG. 1A
has been that, once vacuum is removed from chamber V
1
. the chamber in practice does not quickly return to atmospheric pressure as shown in FIG.
1
B. but continues to have some vacuum pressure even after chamber V
2
has been activated. This extended vacuum pressure in chamber V
1
can result in some lighter articles being pulled against belt
34
and held sufficiently so as to be fed by the belt while chamber V
2
is clearing the leading article, this also resulting in the potential feeding of a double.
Another potential problem is that, in the system of
FIG. 1A
, operator skill is the only assurance that all articles
62
are aligned against wall or fence
32
. This results in some articles not being properly aligned, leading to potential feeding errors. The system of
FIG. 1A
also has potential problems in feeding shorter articles.
A need therefore exists for an improved singulation mechanism which overcomes the problems indicated above, and which otherwise optimizes the singulation operation, particularly in high performance applications.
SUMMARY OF THE INVENTION
In accordance with the above, this invention provides a singulation head for use in a singulation mechanism for flat articles of varying size and weight, which mechanism includes a takeaway mechanism for articles exiting the head, detectors for selectively detecting article position for an article being singulated, and controls for the singulation mechanism. The singulation head includes a selectively perforated belt driven across the head at a selected rate, at least two vacuum chambers positioned behind the belt so as to apply vacuum thereto when energized, the chambers being successively positioned along the belt, with the controls energizing the chambers in a predetermined sequence in response to outputs from the detectors, and a feedback mechanism selectively controlling pressure and/or flow for at least one of the chambers to facilitate the feeding by the head to the takeaway mechanism of heavier articles to be singulated, while inhibiting bleedthrough d

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