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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to conveyor systems and more particularly to a
magnetic conveyor system.
2. Description of the Prior Art
Envelope machines which transform cut paper blanks into finished envelopes
require conveyor systems for transporting the envelope blanks from one
portion of the machine to another. These conveyor systems must be capable
of gripping the blank and holding it in proper alignment during the
transport thereof. In addition, the longest conveyor reaches extends from
the feeder section of the machine which generally includes an adhesive
applying section for applying the closure flap adhesive, through a dryer
section to an envelope forming section. Due to the necessity of thoroughly
drying the closure flap adhesive before allowing that adhesive to come
into contact with other surfaces, the transport from the adhesive applying
section is along a relatively long path. However, during transport, it is
necessary that the blank be firmly gripped to be carried along at the full
machine speed while at the same time maintaining alignment of the blanks
with respect to the machine.
Such transport has normally been carried out through the use of endless
chain conveyors which either have gripping members which individually grip
the paper or are biased into firm pressure engagement with one another
with the paper entrapped therebetween. Such chains are extremely expensive
while at the same time being subject to wear and breakage. When a given
length of the chain has worn and is in need of replacement, it is a time
intensive task to replace the link. Additionally, when the link is
replaced, the resultant chain, due to looseness between other links, may
have a different overall length than initially. More importantly, since
the paper is usually gripped by two chains, one on each side of the paper
so as to leave the adhesive applied flap free of contact, it is possible
that the chains will achieve different lengths. Since the links of the
chain will not be consistent, but will vary throughout the entire length
of the chain due to looseness or tightness between adjacent links and the
tensions applied thereto, it is possible for different sections of the
chains to be moving at different relative speeds sufficient to misalign
the blanks between the parallel running chains.
Of course should one of the links break before replacement, the maintenance
task of repairing and replacing that chain is quite complicated. In
addition, such chains are extremely heavy and require undesirably large
energy expenditures to move them.
While other transport devices, such as driven rollers and the like have
been used, the necessity of firmly gripping each blank and of maintaining
it in alignment without contacting the gummed area of the blank has
required that such alternative transport devices be extremely complex and
expensive.
Although it is known to use magnetism in connection with transport devices,
such uses have either relied upon use of electromagnets to energize
ferrous armatures which will move conveyor bllt backing plates (see for
example U.S. Pat. No. 3,227,344 to Rutter) or they have involved the use
of permanent magnets mounted on a surface for attracting and holding on
the surface metallic members, (see for example U.S. Pat. No. 2,958,019 to
Scholten). It has also been known to utilize electromagnets disposed
underneath a conveyor to attract metallic objects to be carried into
contact with the conveyor surface (see U.S. Pat. No. 3,199,654 to
Buccicone). In addition, it has been known to impart an electrostatic
charge to a sheet of paper to cause the paper to adhere to a specially
constructed conveyor tape (see U.S. Pat. No. 3,761,074 to Benbenek). Each
of the prior art magnetic force utilizing transport systems has particular
advantages and disadvantages. Among the disadvantages are the inability to
transport non-magnetic devices or non-charged devices in those systems
which utilize either permanent magnet coatings to the conveying surface or
magnetic underlayments or electrostatic chargers. Particularly, devices
which rely upon applying an electrostatic charge to the paper are
undersirable in high speed machinery because of the difficulty of totally
eliminating the electrostatic charge at the desired point. Once the charge
has been applied to moving paper, that charge has a tendency to remain
with the paper and will cause the paper to move improperly through other
parts of the machinery and will further cause the paper to adhere to
similar charged papers.
However, a chief advantage of the use of magnetism in transporting devices
is the ability to eliminate heretofore complex mechanical grasping means
or the prior used opposed weight devices or other types of pressure
applying constructions.
It would therefore be an advance in the art to provide a magnetic transport
system for moving non-metallic sheets wherein the magnetic force is
utilized to hold the sheets in place in the conveyor system without
applying a charge to the sheets.
SUMMARY OF THE INVENTION
My invention provides such a magnetic transport system. The invention
utilizes opposed moving surface transport members with the members having
permanent magnet capabilities with the magnetic poles aligned on the
opposed surfaces such that the north and sough poles alternate across the
width of the surfaces traverse the direction of travel of the conveyed
article.
The magnetic poles of the opposed surfaces are arranged such that the
surfaces are attracted to one another to entrap the sheet material
therebetween. In addition the strength of the magnetic fields is
maintained small enough so that there is not a significant force required
to separate the opposed sufaces. However the magnetic field strength is
sufficiently strong to maintain a degree of contact between the surfaces
and the sheet material sufficient to prevent movement of the sheet
material independently of the surfaces.
In a preferred embodiment illustrated, the transport system involves the
use of opposed conveyors each of which is constructed of an endless belt
suspended around and between movable sheaves, with one length of the belt
between its supporting sheaves being opposed to a length of the other belt
between its sheaves, the belts moving around their sheaves so that the
opposed lengths move in the same direction. The sheaves are placed
sufficiently close together so that the belts will normally contact one
another as a result of their magnetic attraction.
In an alternative embodiment, one of the conveyor belts is at least
partially replaced with a rotating cylinder like roller constructed of
alternating magnetic disks and non-magnetic disks.
I have found that such a system works particularly well in transporting
paper, and in particular in transporting paper blanks in environments such
as envelope manufacturing machines. In such a construction, two sets of
opposed belt conveyor systems are used to receive and grasp the paper
blanks alongside edges thereof leaving the intermediate portion freely
suspended between the conveyor sets in such a manner that the adhesive
coated closure flap will not contact any of the elements of the machine
and will be free to dry as it passed through the heated drying section.
It is therefore an object of this invention to provide an improved
transport system for moving non-ferrous sheets.
It is another and more particular object of this invention to provide a
transport system for moving paper sheets by inserting the sheets between
two opposed moving surfaces which are at least partially formed of
materials having permanent magnet properties, the surfaces being attracted
to one another whereby they will grip the paper therebetween.
It is another and more particular object of this invention to provide a
paper transport system comprised of opposed aligned endless conveyors, the
conveyors being constructed of flexible permanent magnet strips which are
attracted to one another and contactable over a length of the conveyors to
grasp a sheet of paper received therebetween for movement therewith, the
strips having the magnetic poles thereof alternating across the width of
the strip tranverse to the movement of the conveyor.
It is again another important and particular object of this invention to
provide a paper transport system utilizing opposed magnetic moving
surfaces disposed so as to be attracted to one another and entrap a sheet
of paper therebetween for movement therewith.
Other objects, features and advantages of the invention will be readily
apparent from the following description of a preferred embodiment thereof,
taken in conjuction with the accompanying drawings, although variations
and modifications may be effected without departing from the spirit and
scope of the novel concepts of the disclosure, and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an envelope machine.
FIG. 2 is a fragmentary perspective view with portions broken away of a
prior art paper grasping chain used in envelope machines.
FIG. 3 is a view similar to FIG. 2 illustrating another prior art paper
moving system used in envelope machines.
FIG. 4 is a view similar to FIGS. 2 and 3 illustrating yet another prior
art method of moving paper in an envelope machine.
FIG. 5 is a simplified diagramatic view of the paper conveyor of this
invention.
FIG. 6 is a cross sectional view taken along the lines VI--VI of FIG. 5.
FIG. 7 is a fragmentary perspective and sectional view of the paper
conveying assembly according to this invention.
FIG. 8 is a fragmentary perspective sectional view of a modified form of
the magnetic strip of this invention.
FIG. 9 (on page 1 of the drawings) is a fragmentary view similar to FIG. 5
illustrating a modified form of this invention.
FIG. 10 is a perspective view of a magnetic roller according to this
invention.
FIG. 11 is a cross sectional view of the roller of FIG. 10.
FIG. 11a is an enlarge partial view of the roller of FIG. 11.
FIG. 12 is a sectional view of one of the magnetic disks of the roller of
FIGS. 10 and 11.
FIGS. 13 and 14 are simplified diagramatic views of combined conveyor and
roller transport assemblies.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates an envelope machine 10 such as in general use in the
industry today. The machine includes a feeder 11, a closure flap adhesive
applying section 12, a drying section 13, an aligner section 14, a window
forming and gluing section 15, a folder section 16 and a delivery table
17.
In use, the envelope blanks are inserted into the feeder which feeds them
into the closure flap adhesive applying section which applies a dryable
adhesive to the closure flap. As is common in the art, the envelope blank
has a width considerably wider than the closure flap and the adhesive is
therefore only applied across the central portion of the width of the
entire blank. The adhesive is applied wet and must thereafter be dried
before the blank can be worked upon by the machinery inasmuch as any
contact between the wet adhesive and the machinery will cause the adhesive
to smear and the paper blank to stick to the machinery parts. In order to
accomplish drying, the envelope blank is moved from the closure flap
adhesive applying section 12 through a drying section wherein heater
devices 19, such as heating lights, will evaporate the moisture content of
the adhesive. During this movement through the drying section 13, the
envelope blanks are suspended between two parallel transport systems 20
and 21. In order to reduce the overall length of the machine, the drying
section is normally located underneath other operating portions of the
machine. At the outlet end 23 of the drying section, the envelope blanks
are moved over a large roller drum 24 into the aligning section 14. Once
in the aligning section, the envelope blanks are acted upon by rotating
dies and the like to be creased for folding. In addition a central section
may be cut out and the borders thereof provided with glue and a
transparent window applied from a roll of transparent film 25. After the
envelope blank has been fully creased, it is moved into a folding section
16 where, due to the provision of adhesive at appropriate points, the
envelope will be folded and fully formed for delivery to the delivery
table 17.
My invention concerns itself primarily with the movement of the paper blank
from the closure flap adhesive applying section 12 to the aligning section
14. During the transport of the blank between these two sections and
through the dryer section, it is necessary that the blank be firmly
grasped on both sides of the aadhesive coated closure flap. In addition,
it is necessary that the conveyor means that grasp it on both sides move
at the same speed so as to not cock the blank with respect to the machine
or to other blanks. Since the central section of the blank must be left
freely suspended and out of contact with any of the portions of the
machine in order to insure proper drying of the closure flap adhesive,
prior art devices for moving the paper have been quite expensive.
One such prior device is illustrated in FIG. 2 and consists of a linked
chain 30 with grabbing fingers 31 attached thereto. As the chain passes
over a sheave, the fingers will lift away from the links 34 to which the
fingers are not attached because of the bending of those links with
respect to the links 35 to which the fingers are attached. When in such a
lifted position, an edge 36 of a sheet of paper, such as the envelope
blank, can be interposed between a surface of the links 34 and the
undersurface of the fingers 31. Thereafter as the chain becomes linear,
the fingers will entrap the paper between the undersurface of the finger
and the surface of the links 34. The use of such fingered chains is common
in the industry for transport through the dryer section. Such fingered
chains are quite expensive often costing in excess of $20.00 a foot. Since
envelope machines in normal use today require over 80 feet of chain per
machine, the great expense is quite apparent. In addition, since
mechanical linkage chains must be used, the weight of the transport
section is undesirably large and the amount of power expended in moving
the paper and the chains through the section is considerable. In addition,
chains present maintenance and replacement problems.
FIG. 3 illustrates another prior art method of moving the paper blanks. In
this construction opposed chain conveyors consisting of two opposed chains
40 and 41 are provided. The paper blanks are received between the chains
and in order to insure that the paper is firmly grasped, weights 42 ride
on the outside surfaces of the upward chain. In addition, the weights may
be spring urged against the chain. In order to prevent the weights from
moving, pivotable linkage arms 43 attached to the machinery base 44 are in
turn attached to each of the weights 42. The chain 40 opposite the weight
associated chain must then be backed against a supporting surface 45.
While such devices work effectively, the friction generated by moving the
chains against the support surface 45 and the weights 42 is excessive and
again requires the application of a high degree of energy input to the
transport system. This friction cannot be eliminated through lubrication
because of the effect of the lubrication would have on the paper blanks.
Additionally, although such common linked chains are less expensive than
the chains illustrated in FIG. 2, they still average approximately $10.00
per foot thus resulting in a large expenditure for the system. Once again
maintenance and replacement problems are encountered.
FIG. 4 illustrates yet another prior art embodiment of a transport system.
This transport system utilizes opposed rollers 50 and 51 with the rollers
51 being driven by means of gearing 52 from a common shaft 53. In such
embodiments, the paper blanks 54 may be entrapped between the rollers or,
as is more common, conveyor belts 55 are provided between the rollers with
the paper entrapped between the conveyors. The use of the conveyors
insures that the paper blanks will not fall between the rollers. Such
transport systems, although requiring less energy than the chains because
of the absence of friction, are considerably more expensive initially, add
a great deal of unwanted weight to the machine and employ and undesirably
large amount of gearing.
FIGS. 5 and 6 show, in a simplified embodiment, the transport mechanism of
this invention. The transport consists of two endless strip conveyor
systems 60 and 61 each of which consists of at least two sheave wheels 62
through 65, the sheave wheels of each conveyor system being positioned at
axial parallel spaced apart relationship with each of the sheave wheels
being rotatable and at least one driven by connection to a motive source
(not shown). Endless strips 66 and 67 are provided for each conveyor
system, the strips being received around the associated sheave wheels and
spanning the distance therebetween. The sheave wheels of each conveyor
system are aligned axially parallel to the sheave wheels of the other
conveyor system and are disposed in aligned planes and positioned with
respect to one another whereby lengths 68 and 69 of the strips spanning
the distance between their associated sheave wheels 62, 63 and 64, 65 are
closely positioned to one another and are opposed to one another as
illustrated at 70. The sheave wheels are positioned sufficiently far apart
so that a paper sheet 71 can be received therebetween and be contacted by
the opposed surfaces 72, 73 of the lengths 68, 69.
The strips are formed of flexible permanent magnet material. This material
is generally constructed of a composition of rubber and barium ferrite
powder and is preferably of the type wherein the magnetic flux lines in
the barium ferrite filler have been oriented to provide a series of
alternating N and S poles across the width of the strip. Such strips are
commercially available and include products manufactured under the
trademark PLASTIFORM by the Industrial Electric Products Division of 3M
Company.
According to my invention, these strips are formed into endless belt strips
with the magnetic poles alternating across the width of the strips
transverse to the direction of movement of the strip. As illustrated in
FIG. 6, such strips are arranged with the north (N) and south (S) poles
alternating across the width of the strip. Preferably the aligned belts 66
and 67 have their alternating poles staggered from one another so that the
imposed lengths 68 and 69 will have opposed poles facing one another at
the surfaces 72, 73. In this manner, the strips will be attracted to one
another and will thus firmly grip the paper strips 71. Whenever in this
specification and the claims appended herto I have used the phrase
"flexble permanent magnet material" it is to be understood that I am
referring to that class of material constructed of a flexible composition
having ferrous material therein which is magnetized into lines of
substantially continuous alternating polarity, the ferrous material being
of small particle size so as to not substantially interfere with the
flexibility of the overall material, substantially as described above.
It should be noted, that as shown in FIG. 6, the sheaves can be centrally
depressed as at 75 to receive the strips 66, 67 to maintain them generally
in alignment. One of the unique features of using strips with alternating
poles spaced traversely of the length of the strip is that the strip
themselves are generally self-aligning in that only the opposed poles are
attracted. By providing spacing between the poles transverse the direction
of movement of the strip, the strips will naturally attract in the correct
aligned condition.
By closely spacing the opposed sheaves, such as the entrance sheaves 62 and
64 shown in FIG. 5 so as to provide clearance for the paper 71, the rows
of magnetic poles running the length of the strip and being spaced from
one another across the width of the strip will cause the opposed lengths
68 and 69 of the strips to contact one another closely adjacent the
sheaves 62, 64 and to be in correct common edge plane alignment. Because
the alignment is created by the magnetic attraction of one strip to the
other, it will be maintained for the travel length between the sheaves 62,
63 - 64, 65.
By utilizing a magnetic field having a sufficent strength, it is assured
that the paper will be fully grasped between the opposed strips and
carried therewith. Because the magnetic attraction has the ability to pass
through the paper, the strips will be urged into tight gripping engagement
with both sides of the paper. In addition of course, those portions of the
strip in intermediate successive strips of paper will be in full
engagement with one another.
However it is to be appreciated that one of the important features of this
invention is the ability to use relatively small strength magnetic fields.
Because the poles continue the entire length of the strip, the actual
force holding the paper in position is the attraction strength of the
strips for the entire length of the paper. Thus the attraction strength at
any given cross section of the strips may be quite small so as to allow
the strips to be very easily peeled apart at the sheaves 63, 65 while
maintaining a very high strength grip on the sheets of paper intermediate
the sheaves.
As is shown in FIG. 7, the individual strips 66, 67 preferably consist of
two layers 78 and 79 with the flexible permanent magnet strip comprising
the layers 79 which are backed by backing layers 78. The backing layers
may be constructed of conveyor belting material, rubber, or the like and
serve to give strength to the permanent magnet strips 79. FIG. 8
illustrates a modification wherein the permanent magnet strip 79 with or
without the backing strip 78 is in turn further backed by a spring steel
strip 80. Also as shown in FIG. 7, if desired the machine on which the
transport system is used may have a rigid backing 81 with a groove 82
therein in which the strip 66 or 67 is received.
As indicated in FIGS. 7 and 8, preferably a plurality of pole lines 90 are
provided on each of the surfaces of the strip 79. It is to be noted that
as illustrated in FIG. 8, the poles run continuously the length of the
strip.
Although it is possible to create a strip having a large number of pole
lines, I have found that preferably the poles should be placed no closer
than one-eighth of an inch apart transverse the strip. The reason for this
is to insure that the strips will be self-aligning with associated strips
as they come into opposition with one another at the sheave wheels. The
reason for the spring steel backing 80 in FIG. 8 is to give increased
strength and wearability to the conveyor inasmuch as the flexible
permanent magnet material presently available does not generally have
sufficient wear qualities for independent long term use as a conveyor.
FIG. 10 illustrates a modified form of the invention wherein the magnetic
conveyor consists of a stack 95 of disks 96 received around a central axle
97. The disks are of two types, those having a magnetic charge 99 and
ferrous spacer disks 100. As is illustrated in FIG. 10, the disks 99
comprise flat disks having a central aperture 101. The disks may again be
constructed of a combination of rubber or other elastomeric material
filled with barium ferrite. These disks normally are permanently charged
to function as permanent magnets with a north pole on one face of the disk
102 and a south pole on the opposite face 103. By alternating the disks
with metallic washers or disks and by reversing the disks 99 so that
adjacent disks present faces of a like magnetic pole to one another spaced
apart by the non-charged disk 100, the resultant stack will have an outer
diameter magnetic polarity with the polarism centered at the center of the
non-charged spacing disks. In this manner, for example if two N poled
fields are placed in contact with opposite sides of a non-charged ferrous
disk, that disk will then have a N polar charge evidenced around its
periphery. Thus by reversing the charged disks and spacing them with the
non-charged disks the periphery of the resultant stack 95 will be charged
with alternate poles in somewhat the same manner as the surface of the
aforementioned conveyor strips.
By then opposing the stack 95 with a conveyor strip such as illustrated at
106 of FIG. 11a, and by spacing the poles of the strip 106 the same as the
stack 95, substantially the same attractive effect can be created between
the strip and the stack has been previously described between opposed
strips.
Since disks such as that shown in FIG. 12 are commerically available with
diameters as small as 11/2 inches and thicknesses of one-eight of an
inch, it can be seen that such stacks can be readily used either
individually in opposition to a conveyor or as a group of parallel rollers
in oppostion to a conveyor.
FIG. 13 illustrates such system utilizing both opposed conveyor systems 110
and 111 and charged rollers 112 constructed according in the manner of the
stack 95 of FIG. 10. In the embodiment illustrated in FIG. 13, the
conveyor system 110 extends beyond the end of the conveyor system 111 and
the rollers 112 are placed under the conveyor system 110 beyond the end of
the conveyor system 111. A paper strip is illustrated at 113 to show that,
due to the small diameter of the rollers, the paper strip or envelope
blank will normally be considerably longer than the diameter of the
rollers and in this manner, it is assured that the paper blank will
continue to be entrapped between the conveyor strip and the rollers and
will not have a tendency to fall between the rollers.
FIG. 14 illustrates another embodiment making use of both opposed conveyor
strips and rollers and the use of a magnetically charged conveyor strip in
connection with a metallic drum.
In FIG. 14, a first conveyor strip 120 is provided which is received around
a drum 121 having a metallic surface 122. The drum may form one end of a
conveyor system 120a with the drum 121 serving as one sheave. A second
conveyor system 124 consisting of a strip 125 and associated sheaves 126
(only one of which is shown) overlies one length of the strip 120 upstream
of the roller 121, upstream being determined by the direction of the
rotational arrows 127. A third conveyor system 129 consists of a conveyor
strip 130 and associated sheaves 131 (only one of which is shown). This
strip is located downstream of the drum 121. A continuous line 140
illustrates a sheet of paper or a stream of individual paper blanks being
moved by the system. Magnetic surface stacks 145 are interposed between
the sheave 126 and the drum 121 and between the drum 121 and the sheave
131. These stacks are rotated in the same direction as the sheaves 127 and
131 and the drum 121.
This system serves to transport the paper through a reverse path while
maintaining it in constantly gripped relationship. The conveyor system 124
has one length thereof 150 attracted to the strip 120 and will grip the
paper 140 therebetween. As the paper passes beyond the sheave 126 which
must be spaced from the drum 121 in order to provide clearance for the
relatively large diameter sheave 127, the paper will pass between the
strip 120 and the magnetic surface stacks 145 to continue the gripping.
Because the stacks have a fairly small diameter, they can be placed
reasonably close to the surface of the drum. Thereafter, because of the
metallic surface of the drum, the strip 120 will be attracted to it and
will entrap the paper sheet 140 between itself and this surface 122 of the
drum. After the paper sheet 140 is moved around half the circumference of
the drum a deflector member in the manner of a doctor knife 152 will
direct the paper to the magnetic surface stacks 145 on the top side of the
drum. These in turn will grip the paper between themselves and the strip
120. The paper will then pass into the opening at the sheave wheel 131 and
be gripped between the conveyor system 129 and the strip 120.
It is to be understood that FIGS. 5, 13 and 14 illustrate only basic
systems variations which are possible utilizing the opposed charged
conveyor strips and the charged surface rollers of this invention and that
other systems are not only possible but clearly envisioned. One such
possible system can use opposed stacks 95 with one stack movable towards
the other. Another system can utilize much longer conveyors than
illustrated with associated rollers for moving the conveyors about an
angle to change the direction of movement of the entrapped paper or other
non-metallic sheet material.
It will be further appreciated that although the flux lines 160 of the
disks 99 normally flow around the periphery from the one face to the
other, that by combining them in the stack 95 with alternating reversed
polarity and interposing ferrous washers the flux lines will flow between
adjacent permanent magnetic disks and will be concentrated at the outer
periphery as illustrated in FIG. 11 at 161.
In addition, although I have described the opposed conveyors as utilizing
sheaves it is to be understood that other types of end rollers could be
utilized as is standard in the conveyor industry. As an example in FIG. 9
I have shown the use of a cogged sheave or roller 170 used in connection
with a strip 171 having a toothed undersurface 172 which cooperates with
the roller 170 in the manner of a timing belt. This embodiment is
especially advantageous where the strips are relatively long and it is
necessary to drive parallel strips at identical speeds without slippage as
in the embodiment of FIG. 1 where the total travel between the adhesive
applying section and the aligning section through the drying section may
be in excess of 20 feet.
Although the teachings of my invention have herein been discussed with
reference to specific theories and embodiments, it is to be understood
that these are by way of illustration only and that others may wish to
utilize my invention in different designs or applications.
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